Follow up with DNA should certainly help clarify any Mediterranean connection. On a related subject, does anyone know about reports by early explorers that the Mandan Indians spoke Welsh, or something with Welsh words? I think that the exact statement was that a Weshman in the expedition could understand/communicate with them. I seem to recall they were quickly wiped out by smallpox.
Now, I've read also that the Lewis & Clark expedition encountered the Mandans and (it was said) did record Welsh words being used by these people.
Also, it is reported that Thomas Jefferson told Lewis & Clark not to mention anything about the Welsh words or any light skinned blue eyed people.
It is also reported that Jefferson's reason was that he was afraid that England would use this connection to make a claim to the western parts of what is now the USA.