Ancient Tribes of Israel in the New World

I have been coming across a few people on the internet (especially on youtube) claiming with quite some certainty and confidence that the lost tribes of Israel are in fact the ancestors of all native Americans. Now I have heard something similar coming out of Mormons who claim that the Book of Mormon was in fact written by such tribes in the 6th century BC. I am open to discuss and listen to as many ideas as you might know of which ascribe to this theory but what I really want your opinion on is why you think such people actually believe in these 'very historically baseless theories' and what you might know they may use as 'substantiated' proof.

As far as I know, these people believe that this voyage of the tribes of Israel to America was mentioned somewhere in the Apocrypha, where exactly, I don't know. 

i personally think lost tribes might have migrated towards several areas, but not so far as north america. i personally thinkthey went towards east and north, areas like turkey, iraq, iran, southern russia, central asia, kashmir, south asia etc.... these areas seam much more reasonable

Well, I actually remember reading somewhere here on AE that there were in fact horses in America but that at some point they became extinct. The problem I think with this theory about the lost tribes is that no aspect of it even makes sense. We know that genetically native Americans were closest to east Asians since there was a major crossing of the Behring strait some time around 40 000 years ago (correct me if I'm wrong).

Secondly, I haven't come across any proof that there was any contact between America and Asia/Africa after the continents moved adrift. Proof for this would be revolutionary in my opinion. I mean, some discoveries were made lately which might imply that contact between people in Europe and the then civilised world may have happened. I remember reading about the discovery of a boy of Greek origin burried near the site of Stonehenge. But then obviously the trip to America is something that requires travelling through an ocean and not only on the coast and I'm sure caravels weren't invented back then.