If Messi played in Italy, there's no way he would score the goals that he does or be the player he is. Tactical awareness and defensive capabilities are just too strong in Italy. Every striker who has played there has said that.
Maybe he would evolve into a different player, it's hard to know. But he is exceptional, and has amazing dribbling skills, and game vision so I think he would still do well there. Also don't forget that every team that plays Barcelona, probably adapts some type of strategy just to play against him, so he still has a hard life on every game he plays.