Pardon the possible thread drift, but I see "Native Americans came from Israel about 2500 years ago to what would one day be the United States" as being no more incredible than "Every animal species on Earth is descended from a M/F pair that rode out a flood on a wooden boat 5500 years ago".
1. Proof: Can we prove that Native Americans are not descended from Semitic peoples? yes -- all the proof: historical, linguistic, archaeological, anthropological and genetic point to that
in contrast -- can we prove the there was no flood that threatened to wipe out mankind? -- there is no proof for it, but none against. And specifically tot he point that every animal species -- the Bible says in Genesis 6:20 Two of every kind of bird, of every kind of animal and of every kind of creature that moves along the ground will come to you to be kept alive not every animal, so of course not the fish. Nor does it specify that every animal species presently on Earth is descended from these, though it is implied.
2. Relevance to dogma -- Let's take Noah's ark's story here. If is it "shown incorrect" does it in any way change Jewish or Christian dogma? No, not really. Is it central to dogma? No.
in contrast to Mormonism, the idea of Semites in pre-Columbus America is central to dogma as that's the theme of the book of Mormon.