Mexican's Favorite Sport

Listen here, you chucklehead. You think you're smart, but you're the kind of person who probably thinks that a 'Mexican' can be used as a singular noun. It's a nationality, not an animal. The joke plays on the word 'cross country', which sounds like 'cross the country', suggesting that Mexicans like to cross the border. It's a pretty low-brow, stereotypical pun. Don't try to act like you got it because you didn't.