I can only speak English like many other Americans but the NA server should probably have more than just English. I have plenty of friends who have Spanish, Korean, Chinese, and French as their first language who live in North America. Not to mention Canada and Mexico are part of North America and those countries have French and Spanish as National languages respectively.
It doesn't make sense to limit language options when they are honestly easy to patch in. Its not like Riot would have to do any more recordings for other languages because they have it done already. It would help ESL players enjoy the game significantly and it would encourage more to actually pick up the game.