Approving a treaty requires 2/3 yes votes. Vote against it requires 60 senators to break a filibuster so 40 wanting it would be able to prevent disapproval and allow it to go into effect. There's a huge difference between needing 67 and 40 to "approve it".
And even if you get 60 votes the president would still need to sign it. If he doesn’t then the Senate would need 2/3 of the votes to override his veto.
Congress has essentially abdicated all its power. The president is king.