If the DNA evidence reported that Jewish or Semitic settlers had reached America, this would not back up Joseph Smith#s claims.
Because DNA or not, Joseph Smith was stil a liar. Joseph Smith created the Book of Mormon. Was it based on several other works? Or did he created it all out of his own febrile mind? It really does not matter because Joseph Smith published the damned thing!
Joseph Smith used the Jewish connection because that was in the public eye. Many people has written or spoke on the subject of the lost tribes of Israel, so it was something for Joseph Smith to latch on to.
But what if Joseph Smith had heard a theory that caught his attention? The theory that people had come to America from Asia? What if he had based his Book of Mormon on Mor mon a Warlord from Asia with his band of followers?
The DNA evidence would have backed up this claim of Smith's even though it was just as bogus as the Semite connection with Lehi and his family.
No matter how you cut it, Joseph Smith was nothing more or less than a liar.