What if I hit a mailbox with my car?

Answer 1

Whoever willfully or maliciously injures, tears down or destroys any letter box or other receptacle intended or used for the receipt or delivery of mail on any mail route, or breaks open the same or willfully or maliciously injures, defaces or destroys any mail deposited therein, shall be fined under this title or imprisoned not more than three years, or both.

Did you hit it "willfully or maliciously?" If not, you are merely civilly liable for damages.