If the only way out is to kill everyone in the USA, this is something that may be attempted at some point. Putin and his new set of weapons could probably razes every major US cities and put an end to the US nonsense.

One way or the other, most humans are gonna die before the end of the century and a dramatic reduction of population will happen. The US way of living will also come to an end, it is simply a matter of doing it voluntarily and aim to avoid the worst or having it forced on them by powers over which they have no say and feel the burn.