America’s error, on a national scale, was the error of the post-WWII generation.
In our nations, we each decided to support the general welfare with largesse, “welfare”, the end result of which created a dependency class.
At the national level, America did this as well to the other democracies, not just offering them “protection” under its nuclear umbrella, but providing for their “defense”, paying for their citizenry to have the protection of our military, instead of demanding that they provide for their own armies to defend themselves.
In the former case, what was created were generations of people who did not work, had little desire for education or self-improvement, and were just public charges. The ambitious among them became criminals.
In the latter case, what resulted were spoiled neo-socialist regimes which used their wealth not spent on defending their nations, into enlarging their own largesse, welfare programs. Had they not done so, the US could have been just another member of NATO, contributing an equal share to mutual defense.
Finally, the chickens are coming home to roost for all of us. Those nations of Europe who fed from the American teat for so long, are now weak before just about anyone who would oppress them, be it Russia or Islam. If it chose to, even the Turkish army could overrun the western half of Europe, even if it didn’t dare treat in the much more self reliant eastern Europe.
“Won’t let us join the EU, huh? How do you feel about western Europe joining the Sultanate?”
Except for those French and British nukes, and the unfortunate fact that for Turkish armies to get to western Europe they'd have to fight their way across a good bit of Eastern Europe.