Whatever we do, let's not blame the killers.
I'm fine blaming the killers, first and foremost. It is their responsibility above anyone else.
However, if Iran gets a nuclear weapon and takes out Israel - it is on Iran first and foremost, but I would also have some significant questions about the actions of Russia and the United States that either contributed to, or failed to stop that action. I would want to know what we plan on doing to stop Iran from doing that again and stop other States from having the ability to do it.
A firearm is a tool, one that needs a person to operate it and needs a person to make that tool fatal to someone else. But without that tool, said person would not be nearly as lethal, would be less likely to act, would be easier to defend against, and (statistically) would even be less likely to harm them-self. Pretending that it is just "people killing people" is not looking at the entire picture: people kill people with guns.
Also, you mentioned cars. Large, fast moving, and while not designed to kill, they are dangerous objects. That we required insurance and a license to drive. So...
States are greater than the constitution... Otherwise the constitution would not limit the power of the federal govt and reserve the powers not given to the federal govt for the states or the people.
You are correct, in that the States have powered reserved to them and the States create the constitution. However, the notion that the State truly operate as independent little nations died with the Articles of Confederation and Perpetual Union. They didn't work. They didn't give the central government enough power to actually govern, so they were scrapped and replaced.
Even when the Confederate States tried to bring back a similar document, internally it was disregarded faster than the Union disregarding the Constitution.
More practically, US jurisprudence predating the civil war made it clear that the Constitution was not "optional" as it applied to the States. The States ceded power to the Federal Government when they ratified the Constitution. To what extent and could that be revoked? Well, that was a serious question - one that the reconstruction Amendments put to bed 150 years ago.
Yes the federal govt assumed its power through blood. The tyrant Lincoln chose to fight a war rather than work out political differences in congress. Lincoln staged the greatest bloody revolution in history. And burned the constitution in the process.
Yes and no. There was no political solution that could be reached to maintain a Union, by 1860 it was painfully clear that such a thing simply wasn't going to happen. The question was whether or not States could choose to leave the Union. That was being debated as cannon balls landed at Ft. Sumtner - at which point, further discussion was moot.
And yes, Lincoln absolutely burned the constitution during the Civil War. He rounded up "dissidents" with no due process, suspended habeas corpus, did plenty of taking (even of Union property) without just compensation, he boarded US soldiers in American homes, he instituted a draft, and on and on and on. Was it better or worse than previous or subsequent wars? Certainly a larger scale than most, but our history of adhering to the Constitution during wartime is dubious at best.
And yes without a central govt we might not be the power we are... But given the founders desire to be free of a central strong government because of the problems they create, wouldn't it stand to reason that they never intended the united States to be the power it has become, with all of its inherent meddling?
I haven't researched nor considered this proposition enough to make an informed discussion. My gut reaction is that they intended for there to be a strong nation, as the founders were the ones who solidified the new, stronger constitution and had a say in deciding to stand up to Great Britain in 1812. I'd have to do a lot of reading with an eye on the subject to formulate a decent discussion.