• Younger generations are less pro Israel.
• There's a segment of liberals that view any victimized or oppressed group as morally superior regardless of context.
• Michigan specifically has a very high population of Muslim/middle eastern descent.
• It's not that sudden, there's been growing criticism and calling Israel an apartheid state for years. The recent escalation in hostilities just made it more newsworthy.

The American left is furious at Biden for the same reason we're angry at pretty much any President's foreign policy. We've opposed most of the interventions and support for dictators that presidents in the latter half of the twentieth century up to today have engaged in. But we have never been the majority, and haven't had the power to stop them. It's important to remember that about a third of the US is composed or pretty reasonable, pro-peace social democrats. The problem is that another third are "moderates" that are okay with empire as long as we pretend we're being nice, and the last third are maniacal religious fascists.

Mainly just due to the recency and severity of the conflict in Gaza, and the fact that it's an election year. Americans never cared when Israeli soldiers routinely dehumanized, murdered, and raped Palestinians in small numbers here and there, but the widespread media coverage of the conflict in Palestine has helped shape public opinion to recognize the incredibly disproportionate response on the part of Israel to the Oct. 7 attacks.

Biden is reaffirming the US's long-held stance on Israel, but it is a stance that is becoming less popular with many who disagree with what Israel is doing. Michigan in particular has a high population of Muslims who turned out in large numbers to oppose Biden, which is why this managed to become newsworthy.

I would also wager a good chunk of this narrative (certainly not all or even the majority, but a good chunk) is likely promoted by Republican-aligned groups who are using this momentum to discourage people on the fence from voting for Biden in the general to help secure a Trump win. Notably a lot of news coverage I've seen lately featured people confirming their plan to vote for Trump, rather than vote for no one, because of Biden's stance on Israel.

Trump himself is remaining relatively tight-lipped about his stance on Israel during this election cycle, despite being a vocal ally of Netanyahu during his previous term, to try to keep the dialog focused on Biden. But it is expected he will continue support for Israel, or even escalate it, due to his previous amicable relationship with Israel and based on how much his voter base likes to dehumanize Muslims (blocking all Muslims from entering the US was an early campaign promise of his in 2016).

So why does this conflict in Palestine in which the US isn’t even an active party suddenly evoke such an emotional response?

Because the US is by all means an active party. The US is selling Israel weapons (including weapons Biden has been bypassing Congress to sell), defending them on the international stage and literally sent them aircraft carriers to prevent anyone in the region from taking action. People have been found guilty in the Numenberg trials for less and people aren't liking the man who's supposed to represent them doing these things.

Can someone explain to me why Americans seem so hostile towards Biden over Gaza all of a sudden?

He proactively circumvented congress to sell Netanyahu weapons that he knew would be used for genocide.

Democrats can always find a lame procedural excuse when there's something they ran on but don't want to do, but when it's something they want to do like enable genocide (and oh lordy do they ever), procedure and decorum evaporate in a puff of hypocrisy and convenience.

Part is the fact that the Americans most likely to be upset by the violence in Gaza are the same that are likely to vote for him. And he's being largely unreceptive to their criticism. In any other election, that would mean his base would probably just let his opponent win. There's an obvious problem with that this time.

Basically, Biden is forcing the nation's left wing to pick between showing their disdain for genocide overseas and stopping fascism to at home. It's not a fair choice and people are bitter about it.

Guess you missed the huge anti Iraq war protests in the early 2000s. And the fact that we've been making Internet jokes about that and George Bush junior since forever.

In the early 2000's we weren't as connected as we are now and people relied a lot more on cable/network news.

But also, and this is really important to understand, the civilian casualties from the Iraq war were over much larger areas, populations, and time. In the same time frame the rate of casualties was far lower. Coalition forces also did their best to avoid civilian casualties by not targeting hospitals, not kettling civilians, and certainly not doing a concerted bombing campaign with large bombs into highly populated areas.

A lot of what's happening with the rate of civilian casualties is because the IDF has thrown all of those protections out the window. They're specifically destroying the food, water, and medical infrastructure of Gaza. When people inevitably try to evacuate they can only do so further into Gaza. The IDF doesn't allow them to evacuate through their lines into cleared areas. This means people can never actually get away from the fighting. Those are all large scale war crimes designed to increase the number of civilian casualties. But they aren't removing troops credibly accused of war crimes from the area either. In fact they've shown no willingness to prosecute tactical level warcrimes such as shooting clearly marked journalists in a quiet area in broad daylight.

Just today the report landed on NPR radio that the IDF opened fire into a crowd waiting for food aid. The IDF is of course claiming the crowd was threatening. But we've known how to securely disperse food aid for decades. Those soldiers may very well have been threatened, but their officers set that situation up. Also of note is just how fast this gets out to the world in the era of social media.

And we haven't even talked about the immense amount of war weariness in the US.

There were marches like, every other weekend about the invasion of Iraq even before the news came out that we were there over a lie. But Bush was president and it was like, "aww... look at the hippies... they think they're helping.. lol!"

Raddatz observed of the 5-year-old Iraq war, "Two-thirds of Americans say it's not worth fighting, and they're looking at the value gain versus the cost in American lives, certainly, and Iraqi lives."

And Cheney's response: "So?"

It was honestly hard to protest when Obama was in office because there were so many frothing racists about that any public protests against the actions of the president would be joined by literal KKK members. But we wrote letters.. oh boy did we ever write letters. Letter writing parties, phone banking about writing letters, sending out mailers with contact info for all of the local reps and higher ups to send letters to, including pre stamped envelopes and form letters to add your name to.

Nobody cared because Obama was so popular that there wasn't really a question of his reelection. Biden is not that popular, the rare opportunity to use a major issue as leverage to threaten a reelection campaign, even if the result of his loss would be dire is why there is so much news about public opinion on Israel/Palestine.

propaganda and division bots mostly.

I mean, the Democrats have been screwing the actually Left for decades now so...

A 100k means Michigan goes red. He's playing chicken with the country at this point.

Who should Biden worry about more?

I think those 726k Trump voters are still winnable if Biden can just move a liiiiittle bit farther to the right.

The choice is pretty easy:

Aid and support to Israel

Or

Aid and support to Israel, and give Ukraine to Russia, and give Taiwan to China, and implement fascism at home

What boils my blood is that everyone kinda accepted right's reaction to the president. For them it's all about theatrics and how much of a frenzy the president can whip with a twitter account, and nobody cares about policies. Biden's administration is incredibly effective, they appoint people when they needed, they organise commissions when appropriate, they propose and support bills and legislations, you know, all the things that presidential administration is suppose to do, and apart from knee-jerk reaction on Israel issue, they were on the right side every time, and they fixed a lot of damage that previous guy made.
But Biden isn't a wanabe dictator that tries to rule around checks and balances to achieve loud social media headlines, so everyone calls him president asleep and waits for Trump but good (and I can't stress enough how bad that would be actually)

I don't find these kinds of comparisons and "latest data points" to be particularly helpful in these kinds of discussions. Voter sentiment is fickle, and how you quantify the "Uncommitted" movement will affect how the data is presented.

We don't know how the Uncommitted will actually vote in November, though we can be certain at least some will not vote for Biden if nothing changes. It's a political game of chicken, and it's Biden's move.

Danger! Danger! Red alert!

Your comment is pretty reasonable but I don't think you're misinterpreting the criticism of Biden here. The US is and has been supplying Israel with virtually unlimited arms and support for decades now. This support has come with very few strings attached. Biden could easily make aid contingent on many of the things you mention, and it would put the Israeli government in a real bind, forcing them to make concessions that their right wing doesn't want to make. Biden isn't being blamed for the whole conflict, and isn't expected to fix it on his own. But he's got a lot of leverage that he refuses to use in the interests of peace. This same problem recurs with basically every president, as AIPAC's influence on the American government is substantial.

Every little counts.