I think that's absolutely right.
Then its a question of how far you want to go back. America has always depended on immigration of one kind of another, so whether it was the first colonialists or later Italians, etc, the people who came here already had the ethic of being willing to travel if that's what it took. Then, once here, we had to travel to develop the full scope of the continent. These ethics would have been handed down, even if only implicitly, from one generation to the next.
What's really interesting to me is that despite this willingness to travel, despite Chomsky's allegations, American citizens have been resistant in general to the idea of 'colonialization.' And this is in contrast to the European powers, who had to be forcibly restrained, rejected, and expelled.
There has got to be something about the de facto '40 hour work week' expectation, too.
Personally, I'd be willing to see a little less economic growth if it meant that it was easier to survive with more free time, etc. I think Americans work too hard.