The more intentionally "scary" the clown is, the less bothered I am. It's the "totally normal" clowns that are freaky. I think it's the makeup. Perhaps a bit of the uncanny valley at play. I also find insane over the top drag queen makeup to be creepy. (Just to be clear, I have no issues with basic drag, crossdressing, or trans people.) It's the over the top makeup that makes them look like clowns or aliens that creeps me out.

Almost as bad as Japan's fear of any outside culture

In the middle of the night, it's darkest hour, I got up in a cold sweat and a swamp of cum. Inseparable, my fear of death came with the lust. I was on a brink, on the edge of doing something to myself, when I brought my partner of ten years a squeaky nose and a palette of makeup. It felt unnatural at first, to have a hatefuck with them, to have a bonner pumped up by my own dread, but I wasn't shy of requesting it again, and again. My phobia got my phalos going like nothing else could. I was not a man I believed I was, but I ran with it anyway.

I have it kind of the other way, a mild caulrophilia. It's just a bit of a bump, but a girl that is already attractive to me, will likely be more so in well-done clown make-up. Which is ironic, because when it comes to normal makeup, I tend to prefer the look of a lighter touch.

Though I think it is probably more about emphasizing and exaggerating facial emotiveness. I tend to have trouble with facial expressions, so when someone can do something to make them clearer, or overact them, it's very helpful/comforting. A clown-girl voice helps too for the same thing. They usually add more emotion to their speaking to go with the overacting.

Actually the characters alot of V-tubers portray is kind of the same thing.

Are people actually afraid of them?

I’ve never really understood this one.

Even the creepy clown trope in horror movies is kinda underwhelming and overdone in my opinion. It feels forced.

I'm terrified of clowns, my wife put on clown makeup one time for a photo shoot and i could not look at her face at all. Just dread.

I wonder what causes it that does not exist within Japanese culture. Is it that American children are potentially exposed to them as children, and circuses just aren't a thing in Japan?

(The fact that children would find clowns scary, having no explanation for such eldritch beings, is not surprising to me.)

I'm not sure that exposure to clowns as a child is as common as it once was, but now that fear of them is a cultural touchstone, our media revels in it and exposes us to explicitely and intentionality scary clowns and nurtures the phobia.