The answer is it's all up in the air.

I expect there's a massive GOP movement to suppress votes and gerrymander other votes. I suspect there are efforts to defraud the election in some counties or even in some whole states. But I don't know how successful they will be.

I expect there will be an attempted coup d'etat if Biden wins the election, but I don't presume it's going to overthrow the US. We may break out into civil war, but then if the Republican party takes power, the US is going to be really hazardous anyway. I'm no expert, but by my understanding civil war is going to be inevitable so long as we can't get relief from the mass precarity and enough election reform to empower the public. And since the Democratic party still treats its progressive wing as red-haired stepchildren who have to dine at their own table, we can expect only table scraps.

Biden staying in the White House means I probably have longer before I'm collected to be processed as an undesirable. It could make a difference of months or decades.

That said, I'm pissed off, too, the degree to which the US is responsible for the Palestinian genocide, though the way I've been following it, Biden has been doing a lot more than the neo-liberal norm to quietly slow down Netanyahu's offensive into Gaza. Not as much as I'd like, by far, but more than I'd expect from an establishment Democrat. Biden's been slow-walking aid to Israel, whereas we expect the Republican party is glad to facilitate massacring Palestinians while simultaneously cutting off support to Ukraine so Russia can take over.

Assuming you are a voter, it's up to you, and maybe it's more important to you to symbolically support Palestine by not voting against the Republican party. But doing so might have material effects that make things worse in Gaza, hence I'm going to vote tactically.