The crazy thing is how young America actually is. If you're 50, you've been alive for a fifth of the time the USA has. I know people who are on the greater side of a third.
But also, 250 years ago we were using horse-drawn carriages, getting dysentery, and dying younger than 40. Now, we literally fly around on triangles faster than sound. We've put people on the moon, brought them back, and sent more. Just recently, we sent people further away from Earth than anyone has ever been. We used to have to mail people things using overtaxed stamps, now we send messages at the speed of light using light.
It's been a pretty awesome quarter of a millennium.