Could be a move that is bad for Boyd's supposed US ambitions, so might shorten the odds of him committing to AWs. He would definitely be an asset, just based alone on video highlights of his exploits with Tondela last season.
Not sure why it would be bad for his supposed US ambitions, he's moving to a similar quality league and should get more game time. Positive move if anything. (not that I think he's actually making the US team regardless).
I agree don't think he is seriously on the Team USA radar, but they would be more aware of him if he was a first team regular at Vitoria (5th in Primeira Liga), rather than shipped off to the 15th best team in Turkey.