What seems least plausible about this to me is that a long period of decline like that (basically what happened to France and the UK) wouldn't result in something like a civil war or other split in the US.
And, no offense, but relative to the rest of the world Americans are kind of old and kind of fat.
So: probably not.
[1] Sources:
https://www.forbes.com/sites/jerrybowyer/2013/07/18/youth-in...
https://www.fragilestates.org/2012/11/25/causes-of-revolutio...