This is all really up to state law, USPS has standards for the mailbox itself but only makes recommendations about what you should put it on. They do suggest that you use a pole that swings away or is knocked over easily to avoid causing harm to people who hit your mailbox pole. This is a distinctly different thing from barriers preventing people from crashing into your house.
I lived in a house on a back road which was a traditional venue for mailbox baseball. The owners put up a very sturdy metal post (some kind of machine tool stand) and a mailbox made out of 1/4" steel. On one occasion I did find a shattered piece of an old 2x4 near the mailbox. Gotcha, you little pecker.
Seems to me like if a person in the US really wants to get a good revenge on mailbox busters, rather than an indestructible mailbox, they should install some cameras good enough to get plates. Vandalizing a mailbox is a federal crime punishable by fines up to $250,000 as well as up to 3 years in jail.