I would think the typical answer is because they weren't as developed, but as far as I know there weren't even ships so they would've been at minimum centuries away from making that kind of journey.
So why first, why did they not have ships? That's probably a pretty common question.
And second, was there ever any written accounts in the Americas of someone at least wanting to make a journey across the Atlantic?
Was Native American seafaring more primitive than early Polynesian?