Military aviation:
Lowest Kill ratio of 20 to 1 in aerial combat says it all.US pilots are the best(they have the best training,the best aircraft,the best everything).Up against their nearest competitor,the RAF,the kill ratio would probably drop to 5:1 but we're unlikely to ever test that theory.
Civil aviation:
Flying started here.We've been flying longer than anyone else on the planet.Our airlines are huge and our safety record is second to none.Licensing standards are adequate but you need much more than an ATP to get a real job stateside.Type-rating standards are the toughest;the 4 hour oral to gain a type-rating is far tougher than the multi-choice questionnaire favored by some.
Thats the generalization;in reality there are just good pilots,average pilots and bad pilots.And all countries have their fair share.