Whenever I see this line of reasoning, I think of the counterexample of the island of Crete. The Cretans have always had a traditional gun culture, in some ways comparable to that in the U.S. There are plenty of guns there that were left over from WW2, and more that have arrived more recently. Now, bear in mind that Greece as a whole has some rather draconian gun laws. Only shotguns are allowed for hunting, pistol permits are extremely hard to get, and rifles and machine guns are banned completely. The Cretans ignore these laws with impunity. Even the local police turn a blind eye to violations. Recently, the government deputy minister of health, a Cretan, was videotaped openly firing his unlicensed pistol into the air during a holiday celebration. He made no apology, nor was one expected.
You can't fight the ingrained culture, and the U.S. certainly has an ingrained gun culture. It's the antis who are being unrealistic if they think they can negate this. And of course we have the great example of alcohol Prohibition. Not only was it a failure as a social experiment, but it had collateral effects, such as the rise of organized crime, that we are still feeling today. A gun ban would be even worse than Prohibition regarding these collateral effects.