I am not saying he would or wouldn't..
I will. Viera has 0.00% chance to be a beast in MLS.
I have watched his games (when he plays) very closely over the past 3 years. He's shot.
In MLS, he would have the soccer intelligence over just about any player in the league and that would make him usefull. He knows where to be, can still make passes and is a threat in set pieces because of his size.
His legs are shot. He can't get upfield quick enough to join the attack and can't track fast guys enough to use his physical frame anymore.
He moved to Inter & Citeh on sheer reputation, and plays an occasional game when the coach throws him a bone.
At this point of his career, he can be a useful MLS player. Think of a guy who does the "little things" to help a team be better.
But in no way, shape or form can he be a beast in MLS. This is from actually watching him play.