Don't tell your son the REAL reason how America became more powerful, not at the age of 7, because it's littered with the disgustingness of almost wiping out the entire Native American population, forced slavery (Blacks, Chinese) to build our infrastructure, and the destruction of other people and nations that don't agree with how we think they should live.

It's ugly, boorish, and later on we're probably going to pay a high price for our stupidity.

Tell your son he is one of the lucky people in the world. That he was fortunate enough to be born in a place where drinking water is plentiful, and where he has a chance, if he works hard, to "be" something. Tell him those things, then go outside and throw the ball with him.