Well, I suppose I better chip in a little bit here.
What protects guns in America is as much the ninth and tenth amendment as much as it is the second. The ninth amendment basically says that "just because we didn't give a certain right to the government, does not mean it's restricted from everybody else". The constitution does not give the government the right to mess with people's firearm ownership, which implies that firearm ownership, is, indeed a right that people have. The tenth amendment says that "anything that we didn't tell the federal government that it could do, is a right reserved for the states, and for the people". This means that there can never be a federal law regarding something over which it does not have an enumerated power. As if that wasn't enough, you can go ahead and tack the second amendment on there, and you've got 1/3 of the bill of rights that goes against federal regulation of firearms.
Now, states, on the other hand, is a different issue. I just moved to a new state, and the gun laws are surprisingly different here. Back in Minnesota, you could basically buy and sell guns on a handshake. In Illinois, all guns of any type must be registered and the bearer must have a Firearm Owner Certificate. As well, the statehouse said that municipalities can make stricter laws, if it likes. This has resulted in the city of Chicago banning guns altogether.
Anyways, now that I've got a bit of clarification out of the way, I'll put my opinion in on a specific issue: assault weapons.
The Federal Assault Weapon Ban was written in 1994, and somehow snuck by the courts. While sounding good (I mean, assault weapons are bad, right?), it was very poorly legislated. Basically, it banned a rifle if it had two (or more) of the following:
* Large capacity ammunition magazines
* Folding or telescoping stock
* Conspicuous pistol grip
* Bayonet mount
* Flash suppressor, or threaded barrel designed to accommodate one
* Grenade launcher
Which meant that an otherwise legal rifle could be banned if it had a bayonet lug and a pistol grip. Weapons with these two features are, of course, America's greatest threat. As well, it banned pistols that had magazines that attached outside of the pistol grip and weighed more than 50 oz (1.5kg) unloaded. This meant that the deadly scourge that congress was trying to protect against was this assault weapon:
(I believe this 1896 invention also breaks the "high capacity magazine" rule with 10 shots, making it more deadly than an AK-47 in the eyes of this piece of legislation).
In any case, this law basically was designed by people who had no clue what guns were, or what made them dangerous, but wanted to look "tough on guns" anyways. Thankfully, this law "timed out" in 2004, never to return.
In conclusion, as someone who knows things about guns, and what makes them dangerous, it's really frustrating to see congress pull stuff like this off. Fear of something is a bad reason to pass a law to ban it, and it drives me nuts when people have just barely enough information (like a few callously thrown around statistics) to think they know what's best for the country.