As an American citizen, you have every right not to vote. But, even if you don't agree with the two leading candidates, and would rather not vote for either, you can still vote for a lesser known candidate. This doesn't mean that the candidate you voted for will win the election, but it's better to vote for who you truly want to win than not at all. Your opinion matters.
Because if nobody votes, why should we even have a right to vote anyway? The government can easily pic a new president themselves.
We wouldn't want that, now would we?
I'm a bit late anyway, just offering my two cents...