Isn there genetic evidence that conflicts with the Mormon claim that the Jews migrated to the Americas around 600 B.C.?
Yes. The Los Angeles Times for February 16, 2006 had a lengthy article giving the scientific data showing that Native Americans are not of Hebrew ancestry but instead are of Asian descent. As a matter of fact, archeologists, biologists, and linguists have all presented overwhelming evidence that physical factors, along with cultural and linguistic ties and molecular data, all indicate an Asiatic origin for Native Americans, not a Hebrew one.