@neolex,

A few possible reasons come to mind:
1. Capitalist culture is by nature outward directed. Dr. Johnson said “A man is never more innocently employed than when he is making money.” That makes honest commerce as such unselfish and moral. A good salesman really gets to know his clients.
2. Americans still hane the predisposition to think of themselves as favored and coming from a protected place. Paranoia is a fringe element in American politics. The fact of the enormous struggles we have faced still does not change the confidence with which we see ourselves.
3. The effects of the Protestant Great Awakening in shaping the national character probably had some impact on how we are willing to understand foreigners. Wesleyanism had a similar if smaller effect in England.