Ballots typically do not have "none of the above" options on them. This has a few consequences.

You can put in "noone" in the write-in, but someone could legally make that their name. Not a valid way to mark none of the above.

You could leave the entry unmarked. However, that is also ambiguous. Did you really mean to leave it unmarked, or did you make a mistake? It also leaves the possibility that someone could put a mark on there for you after the fact.

Because of the lack of voter id, and problems such as ambiguous ballots, how would you show there was fraud or not unless you caught someone red handed? Of course, if you don't need to show an id, how would a monitor prove that the wrong person is voting. Some states do require an id, by my state does not and there are always strange unexplained results.

Oh, that's right. I forgot the US has widespread electronic voting. I was thinking of normal paper ballots where you can just spoil the ballot by scribbling all over it instead of ticking a box. I guess that makes it more difficult to submit a spoiled vote.

That said, you can still vote for one of the lunatic fringe minority parties. Under the American two party system none of them will ever amount to anything.