To the contrary, I'd say American identity is a poster example of fostered identity.

It began with an elite of mostly Enlightement secessionist colonialists (AKA "Founding Fathers") positing a union of British colonies with a liberal constitution, and getting the majority to adopt it (in their own way, even most the then absolute, now relative majority of Christian fundies).

It continued with the expansion of Northwestern industrialism to the West and (after victory in the Civil War) the South, when the agrarian ideal of probably most Founding Fathers was subdued across the country by the merchant ethos, and government-pushed development of railways enhanced mixing.

The last two, and strongest, instances of fostering identity are again federal government pushed policies.

One was the FDR-time war drive, with the draft and war propaganda as main elements: the mixing of grunts from everywhere for a common American cause did forster community, and by design.

The other was the conscious policy of suburban development from the Truman era: in a country with similar-looking rather than regional-specific roads, houses, offices, shops and restaurants, where habitation is so uniformized, moving around is rather easy in a psychological-cultural sense, and minds get uniformized, too.

To be honest, I don't want a fostered European identity like that. I'm fine with an identity existing across a regional diversity, like those earlier developed in Germany, France or Spain, and obviously already developing for the EU.

_{*Lunatic*, n.
One whose delusions are out of fashion.}