Maybe bc americans WON'T and SHOULDN'T settle for a decline - they should violently rebel against this mindset and claw they way UPWARDS - there's more room for more growth, even if you lose #1 status and have to settle for #2 for a while you can still catch up etc.
It's good that at least the US and China are NOT infected with this degrowth and "cyclical history" mindvirus that seems to be doing the rounds in Europe and elsewhere... keep being a bastion of endless progress brothers, fight the good fight! There's a whole light cone to eat/infect (if not for us the for the successors we'll build)! Whoop, whoop!
Jokes aside though, most of the open world we live in today owes its existence to ideas, mindsets, $$$ and tech exported from the US, and I'm sure there's way more cool stuff to come from you once you properly clean up the parasitic individuals and institutions that have infected your society. Purge on and keep growing, fight for a deservedly big chunk of the Dyson sphere and beyond!