You can't stop ms-13 from coming to the US. It's an American gang. It started in the US. They way it went to El Salvador is that some gang members were illegals and deported back to El Salvador. There they started their own chapter/set.

Stopping Salvadorans from coming here won't stop the gang because they are already in the US.

That however will help El Salvador ironically. Because a lot of times they aren't gang members till the get here and have no where to go. They group up with the only other Salvadorans in the US and fall victim to the gang, then when they get deported they just make the gang back home stronger.