You jest, but if you've ever seen a wounded animal fighting like mad for survival, I wouldn't be so confident that won't be the exact same things that's going to happen.
In the case of my country, USA, we are the ones wounding ourselves. We made the conscious choice to elect a government that prefers isolationism to economic competition, and which rejected near-peer military preparedness in favor of more deadlock wars with third world middle east countries. It’s not like we were somehow victimized by the EU.
You don't have to look into the animal kingdom, history works too. No ruling empire has fallen silently and without conflict. Changing the world order always included an aggressive transfer of power