Oh boy, I'm going to need some popcorn for this one.
Don't get me wrong, I do understand somewhat of how people outside the US feel about America's firearm proclivities, but there are some fundamental cultural and legal aspects you are missing out on.
So, firearms that are introduced into commerce in the US are required to have a serial number. This number officially isn't tracked in any database, and by law the federal government cannot maintain a list of who owns what. They find other ways around that law, but the amount of paperwork they have to process to pin anyone down to any firearm can be pretty crazy. Much of the firearms sales records in the country are paper records, so when the ATF does a trace on a gun, they have to comb through their paper database, find the store that sold it, and ask them to look through the stores records to find the private buyer, and go from there. A serial number that has been destroyed or obliterated is a big no no, and you cannot have one reissued to you, because that breaks any sorts of traceability. The said, there are legal ways to have an unserialized/unmarked firearm in the US. It is still illegal for felons to be in possession of firearms or ammunition, but there is nothing physically stopping them from making their own firearms. If they can't make them, they will buy them on the black market, or steal them.
As far as a national database, an official one will be very unpopular, because there belief in the US gun community is that registration is a necessary step towards total confiscation. Considering that our war for independence started when the British tried to disarm a local militia, confiscation won't go over very well here, and neither will registration. Colorado can't even enforce it's magazine ban and universal background check.
Creating incentive structures on purchases through taxation is troublesome, from a legal standpoint. You cannot impose taxes that would have a chilling effect on the free exercise of a protected right, in theory. In practice, they like to pretend that the 2nd amendment, which happens to be pretty fucking clear in it's meaning, is an orphan when it comes to legal protection in the courts. People treat it like an absolute bastard of an amendment, making up complete bullshit to help achieve the interpretation that they want. But anyways, there always be ways around stupid laws and definitions like that. People will make a "hunting" rifle variant to a avoid the tax, but the rifle will be trivial to convert to it's "assault" configuration.
As far as getting people to buy "less lethal" weapons, good luck. Firearms exist because they are a tool designed to apply lethal force. Lethality is their raison d'etre. Practicality is determined by other factors, not lethality. Generally, if it is a defensive firearm, you go with the most lethal option that is in your scope of "practical".
Everyone thinks there is this massive gun crime problem in the US, which is what people would assume after hearing about these mass shootings. The actual numbers are very different. Firearm related deaths aren't even in the top 10 causes of death in the US, and way less than that if you take out suicides. We have over a hundred million gun owners, with close to five hundred million guns in the US, 46% of the total number of firearms in the world. We have 30,000 gun deaths of all types annually. Suicide is more than half, and if you take it down to just homicide, it's about 12,000 deaths. The kicker is that 8,000 of those are gang related shooting in certain urban areas with handguns. The same urban areas that have the strictest gun control laws in the US, and has been run by the same party for 60 years. The same party that wants more gun control on a national level. It's been a while since I've seen the numbers, but that's the rough breakdown. So, I don't really see a 0.0024% rate of firearms to homicides to be a problem. If anything, it's pretty fucking amazing. And it's not one firearm per homicide, either, so the actually rate in lower still. Basically, +99.99% of guns in the US will never be used to take a life. Guns are not the problem.
"See something, say something" they say about red flag laws, unless it's the son of some radical islamic imam training kids in the New Mexico to commit school shootings. If that's the case, they will just dismiss the charges and sweep it under the rug.
I don't see 60 rounds mags much. SSO guys in recent competition used RPK mags on their AKs. Competition is a tournament among special forces units dedicated to the 45th anniversary of the formation of the Directorate “A” of KGB, now part of TsSN FSB.
The left creates a narrative of "white males are the real terrorists" because it's part of an identitarian push to give their voters a unifying enemy.
The left is big about unity and bringing people together to vote for a specific party. To do this they need an enemy, and you can't make an enemy out of people who are already likely to vote for your group.
So you create an enemy out of a group that's least likely to vote for you in the first place.