you really think US soldiers will kill their own countrymen if their not at least getting paid?

Yes. When the moment comes, the US ruling class will use every tool available as reaction to working class movements. They obviously won't escalate to that point immediately, they know it would amount to a civil war. But that doesn't mean the steps necessary to protect bourgeois rule will not be taken and probably will be accepted by a significant amount of the US population. Already the US government has and is using huge amounts of violence to pacify protests and uprisings via the police or the national guard. If necessary, all it would take them is to call a revolutionary movement anti american, or terrorist, or foreign backed, or anything that helps justify the use of military force. Easily they can blame it on Russia, or China, or Cuba, or whatever they don't like, and then the escalation will happen as necessary. Anyways, before any of that happens, the US political establishment has proven to be very good at killing domestic revolutionary movements. Before the tanks start rolling on the streets (ie. Civil war), the US will use paramilitary means to crush the revolution. That is the police, the national guard, the CIA, or even far right shock groups. You mention the way the inflation in the Weimar republic went, but you have to remember how it ended. The left in europe and Germany thought that the sharpening contradictions would lead inevitably to socialist revolution, but instead it ended up in the most vile and brutal reaction by the bourgeoisie. The only thing America differs in that regard is that right now it seems they lack a clear Caesar figure, a person or group that unifies the factions of the ruling class against the bigger threat of revolution. The closest thing to it is war, but it isn't as sure a force as fascism to hold together the bourgeois state. That's something in my opinion the communists in the US could use, but the window of opportunity to do it is narrow before someone comes to the front in the class war and plunges the US directly into full blown fascism.