I am not sure Biden will win. I think he has damaged his candidacy very badly.
But Trump is such a threat that there will be many who will vote against him regardless of who his opponent is. So some resilience there at least.
For Europeans, a Trump win would also be a catastrophe. We have to assume and prepare for the fact that he will win. And that the US will exit NATO and refocus on China. The logic of a Trump presidency is that Europe will rearm and will no longer be your natural ally or you ours. China will not be unhappy at the end of the west, of course. It will make friends in Europe, leaving the US isolated in its anti-China stance and enormously weakened. Knowing how fickle the US is, Japan, Taiwan and South Korea will realise they need to accommodate China. Russia, meanwhile, will chip away at eastern Europe.
Predictably, a much more unstable world.
It's alarming that the Dems haven't got a candidate who can think on his feet.