Yes, he had time to shoot those kids multiple times. That's a big fat, "Whatever". They were likely dead after the first well aimed shot.
To begin with, your callus attitude towards what happened in that classroom is astounding. It is indicative of why this "debate" is so futile. You appear to feel nothing for those kids and what they went through - whether they were killed after the "first well aimed shot" or not.
That said, let me try to get past your perhaps unwitting ugliness and address the points you tried to make.
First you dismiss any effective difference between, for example, a bolt-action hunting rifle and a semi-automatic assault weapon. Fine, so why would anyone need a Bushmaster? If you can shoot a deer or an intruder with a bolt action or shotgun and get the job done just as effectively, why do we need semi-automatic weapons at all? Convenience? Not good enough. Cool-factor? Not even close. So I would suggest that you explain to the world why exactly we need such weapons in the hands of civilians in the first place.
Second, you claim that because there are 200 million weapons out there already, "The crazy people will get them and there is nothing you and I or even Congress can do about it. Period." Really? So if no new semi-automatic weapons were manufactured or imported for civilian use, would there still be 200 million weapons out there in 10 years? 20 years? Would you tell a newborn that there's nothing you or anyone else can do about guns because it wouldn't help anyone right now? Sounds like a rather short-sighted view of the world. Perhaps you would reconsider if you added confiscation regulations as well - but no, of course not. That would be "treasonous" and cause for another "revolution". And at the very least, it would not get past the House with its current makeup. Another reason to vote Democratic in 2014.
The rest of your reasoning is somewhat less coherent, but I will address a little of it.
If someone can afford to spend their money on drugs, they can certainly afford to buy a gun on the black market.
This is a bit of a digression, but I believe you misunderstand why people buy guns on the black market. No one who can "afford to buy drugs" would buy a gun to get more because they already have the money to buy drugs. Based on how you talk about drugs I do believe you when you say that you've never smoked pot in your life. Moreover, the fact that you place the words pot and guns in the same sentence implies that you have a very shallow understanding of what makes someone commit a gun crime. Pot is almost never the source of individual crimes on it's own. Mainly for the reason you yourself suggest - it's too easy to get (Cartel violence is of course another story, but the legalization and regulation of marijuana is a completely different discussion that is also being had across the nation). Heroin, meth, cocaine, etc is where the gun violence is at, and most of those crimes are committed using guns that were purchased legally and then fell into the black market. But back to your case.
I've never owned a gun in my life, and I am certain I could, with a reasonable amount of money, get my hands on 2-3 handguns, unregistered and ready for some school rampage.
And why is that exactly? Because criminals are so good at working the system? No. You can buy an unregistered firearm precisely because so many unregistered weapons are being sold legally. What do you think they're doing at all those school gymnasium "gun shows"? No background checks. No registration. And if you're referring to the weak serial number system currently in place, how about some microprinting on them guns? No of course not, because that would make George Washington cry.
the culture needs to change, and then the people will hand in their guns on their own unless they actually need them
There was a story a few years back about a psychiatrist who gave car companies advice about how to sell all those giant "cars" (e.g., the Suburban) that the government taxed like light trucks - making them VERY profitable. Most people recognized them as gas guzzling behemoths, but this gentleman suggested that if you make them seem like essential utilities (hence Sport Utility Vehicle), people would see them as a way to be "prepared" for anything that they may be up against "out there". After that, you'd see commercial after commercial depicting some suburban family hitting the road with the kids in the back and finding themselves on top of some mountain somewhere for a picnic. Or fighting through two feet of mountain snow. People were being fooled into thinking that they needed these things even though they would never even see a dirt road. (Unsurprisingly, car dealers won't even give you full price for an SUV trade-in if the vehicle shows wear from off-road use). Why would you ever think that, given the way the post-Newtown NRA has gone all the way with "More guns are the answer", guns would ever be marketed or even remotely considered as "unnecessary". No way. Wherever there are people who believe pot smokers go out and buy guns because they can afford drugs, there will be people who think guns are necessary.
Europeans take it as a point of pride that they can't get guns. That is the difference, not how many bullets you put in a magazine.
Not sure what that means exactly. Are you saying that they're socialists? That the US gun culture will never change because people in the US dont work together? Perhaps what you mean to say is that they have gone through numerous bloody wars where guns were used to commit all sorts of heinous crimes and they had just about enough. That the US has been the world's number one gun dealer for a century and has developed a fetish for something that most people have no direct experience with (and never will - shooting ranges dont count). That gun sales to individuals has skyrocketed over the last few years due to "survivalist" notions fueled by a black president and an increasingly diverse population (remember the utility in SUV?).
I understand that you're trying to make the point that all this talk of regulation is futile because it's too late. But you're wrong. It's never too late to plan for the future. From environmental policy to education to drug policy to gun control, it's always too much to sacrifice. Short-term thinking is what's killing us. Not individualism.