You can own a bazooka in the US. People do. It's a destructive device, the rockets are destructive devices, there's a $200 tax on transfer and a limited supply on the market but it's pretty trivial to get a hold of one if you have the money. The world has not yet ended due to bazooka-related chaos, in fact AFAIK they have never actually been used in a crime.

One of the really important things to clarify in gun control debates, I think, is how much is actually legal. It's pretty central to the state of gun ownership as a social phenomenon, and people who live in cities or run with non-gun-owning crowds tend to be pretty oblivious as to how the law actually works. The whole discussion becomes a lot less hysterical in nature once everyone recognizes that there's a substantial number of civilians (often very crazy civilians) who own legal machineguns, tanks, bombs and mortars out there, yet violent crime involving any of those is essentially unheard-of.