Of course it isn't the supreme law of that land. It is a piece of fiction that draws legitimacy from people's belief that following it is more to their benefit than not. As the Constitution, or it's creative interpretation, makes that less and less true, so it becomes less and less able to command that belief.
Your Constitution is flawed because it neither anticipated the formation of nor the deep partisan entrenchment based on political parties. Nor did the framers, through no fault of theirs, anticipate the kind of media environment we have today. The amendment process is consequentially designed to be so slow as to render it incapable of producing solutions to urgent problems.
If you don't like the Constitution, you don't like the United States. Take your ball and walk. You're the one like a broken record, refusing to accept that there are just things that will remain, and Americans will continue owning guns.
To force Americans to do otherwise is un-American, and any attempt by the gov't to do so would immediately cede its rights as representatives of the People.
People who use tragedies to try and take away peoples rights are as close to actually evil as I accept exists in this world. And people who use tragedies to try and undermine the spirit of a nation are even worse, because it's readily apparent they've no desire to actually fix problems, merely to push their morals onto others at the others' expense.
Go back to your make believe world where up is down, left is right, and women are men.