In a more serious answer, the US has a pretty concise constitution and there’s a lot of room for interpretation and laws to fill in the gaps. The specific section leading to this is our second amendment, which is an amendment about militias (in Revolutionary times this seemed relevant), and as a consequence of the need for a militia, about the general public being able to “keep and bear arms” in service of said militia.

The long-running debate is that since militias are obviously anachronisms that have been replaced by standing armies (the closest thing we have to militias is the National Guard, which isn’t really that close at all), what is the point of an amendment about militias?

The answer is amendments to the constitution don’t have to have a point. So this right to “keep and bear arms” has been (after decades of legal wrangling) fully detached from the non-existent militia, which also means that the “well-regulated” clause about the militia has been completely ignored in favor of “completely unregulated” assumption about the arms themselves, and here we are today.

And enough people have been sold on this gun-owning fashion/lifestyle (where entertainment and hero fantasies almost fully replace any actual utility) that between them and the lobbyists for gun manufacturers, there’s no way to impose reasonable regulations on guns in the US.