The US were a blank page, with roughly the same crowd starting with the same common goal and aspirations. Europe comes with 15centuries of nationlike structures and history. Latin and AngloSaxons have very different approaches on life and work (particularly visible in the “PIGS” recent controversy...).
As someone said, you cant make the european omelette with nations hard boiled eggs.
The mere facts that the euro bank notes has zero european symbol (because they couldnt find one) speaks for itself. So they put bridges and windows... India has Gandhi.