It’s not about age. The US is a blend of cultures without a real single identity. It is very different than say Brazilian history, which is much older than the US.

Brazil was originally settled by stone-age tribes. In 1500, Portuguese explorer Pedro Alvares Cabral arrived in Brazil with 1,200 adventurers. Cabral claimed Brazil as a colony of Portugal. The first settlement was founded in 1532. Which is a few hundred years sooner than the US and not established with multiple peoples she cultures.