there's only one hypothetical there: the potential of a big GMD that hits the US - everything else is a given after that.

I'll let you do your own research on how often these occur and at what magnitudes.

I'm sorry to say it's not in the same ballpark as aliens. but the good news is there are defensive measures possible to put in place beforehand that almost entirely mitigate the danger and they don't even cost that much. but there's only political will in thus country to do partisan, divisive shit. and if you talk about solar flares people look at you like you're crazy