There were super powers ways before America was conceived , breh. The rest of civilization kept going right after they all failed. Why should this one be any different?If America falls, being on an island won't save you.
Like I told this crazy ass chick I was trying to fukk when she went on her "new world order" rant: We been through many so called "new world orders" before and guess what, mother fukkers: WE'RE STILL HERE. And we will continue to be"
So all these super powers at the top can continue to blow each other up as they wish. The human race will continue on.
Personally the scenario I think about is the US, and China, Russia and all the other European powers beating each other to the point where they all get so weak that the only remaining thriving societies are those of Africa, where it all started thousands of years ago.