I don't think us Europeans (or many of us) understands where the need for weapons in the US comes from as many or our wars were fought by hired men (mercenaries?), hired by our kings to fight against each other.
I feel, though, that I understand this need a bit better, ever since I was an exchange student in the US 25 years ago

and took a US History class. The US citizens need to own guns & rifles has come, as I see it, from the fact that the US has been somewhat un-evenly settled. And in the big woods or on the open prarie, you'll need a good shotgun, or rifle to protect your & your family, if not from anything else, then from wild boars, bears and such nasty things. In the old days, the country's (USA, that is) defense also rested on the militias that could be formed by & of the people.
I don't think that the founding fathers thought that it would to come to this: that every man and woman in the US can go into to a gun store and buy military equipment such as an UZI Machinegun or an AK 47 (kalashnikov) rifle.
Way back in the early 1800's, people only had flint guns or flint rifles...not the modern type of rifles you can buy today...
I have to agree with the NRA, though, when they say than 'guns don't kill people. People kill people', since it is people who are mad at other people
who kill people. However, when people will kill people

-- it is usually not a good idea to give them easy acces to buy weapons, as there are in some states in the US.
I don't think that it will be good idea to have a restrictive a gun-policy in the US as in Europe, but I think that it will be a good idea to make it harder for people to buy guns. Especially former criminals, and people who mentality disturbed or to use a much older frame 'mad as hatter'.
As for Al Gore's movie, I have seen bit and pieces of it in an Oprah Show (yes, we get Oprah here in Denmark, too). And I have to say that as Dane I'm not impressed. The presentations is very loud and noisy, and doomsday worthy. However, as Dane, I have learned to be critical of everything, even a movie whose message, I basically agree with. And I don't think the movie will convince the skeptics as Al Gore seems to be talking to his own, or preaching to the choir...