It's not about Europe. It's about the massive fuckton of TS//SCI shit shared directly with FIVE EYES and NATO, which shows the exact locations of US strategic nuclear weapons, strategic weapons protocols, intelligence gathering techniques and sources, etc that can almost immediately be sent directly to Russia and China as soon as the US walks out the door. It's about the first line of defense missile detection radars, the cryptologic keys, Global Campaign Plans, Contingency Plans, PBNZ coordinates, non-overflight coordinates, FLAGWORDS, etc.
And that's not all - you also lost all international trade, everywhere, forever. Bye-bye middle eastern oil and Chinese manufactured goods, because all your oh-so-friendly shipping lanes and freedom of the seas is now contested waters full of could-be-privateers. If the EU, by pure necessity, pivots Eastward into a pan-Eurasian bloc, that's game for the US.