Interesting point

Neri must be wrong about the time of Fabrizio's arrival in the US. He said 1956, which is after Barzini's death. Now would the new head of the family really bother with this small fry especially after Michael lived and went on to kill their boss??

So clearly he must have been brought over fairly soon after he did the car bomb, by Barzini himself, before hearing that Mike didn't actually die. I think when Michael saw him running - he ran off directly to sanctuary with a Barzini representative and straight to America there and then!

If he didn't Tommasino would have located him and had him killed!

Calo had no interest in going to America at all