Ronaldo has to adapt alot more with his NT then Messi.
Messi still is the free roam #9/#10 like he is at barca. He has a highly skilled team that doesnt rely on him to go forward. His role can be similar to what its today (obviously, it was different in Xavi's barcelona)
Ronaldo on the other hand, thats a different story. At Madrid he plays in a team that can totally build and create and have reference points so he can play that roaming leftwing role in which he's probably the best in history. He doesnt need to be present and active, he can controll the space and show up where and when he wants, and his goal+assist record confirms he's ridiculous at it.
At Portugal, there is no reference striker, barely central playmaking. He's needs to play a completely different role. He's the main guy everyone tries to reach, he needs to be actively involved in the play for it to proceed. If you keep ronaldo out of the game, portugal is nothing.
Ronaldo suffers a HUGE deal of Portugal not having a centre forward. If they'd had Postiga and a playmaker like Deco today, Portugal would immediatly become a freightening opponent, cause he could again be popping up when he wants, not when he needs.