We often make these arguments to suggest that laws wont make any difference because you cant change how people feel. You only have to change how they behave. So the seat belt law did work; banning smoking in pubs was enforced properly (even in Ireland) and people did eventually get used to decimalisation.
It doesnt change overnight but it does change. If there is a genuine homocidal tendency within the average american then it wont change that. After all, if you are willing to break the law by killing someone you are unlikely to be concerned at breaking the law by leaving house with a weapon.
As someone else said, americans dont want it. THey love their guns. I suppose it is none of our business really.