Probably doesn't matter much.

Can Europe become productive again? Sure, they've done it thousands of times.

Can they build a navy? Probably, but should they? Unclear. It's looking like big ships are big sitting ducks.

American protection was a double-edged sword, Europeans had to entertain American ideas of morality -> e.g. importing migrants against their best interests.

Lose NATO, lose the USD system, people who work and produce things will probably benefit no matter where they live. Big losers will be people who produce nothing and live by their political opinions.