Law is class power, so we have to ask why the ruling class of the US wants its working class to be armed.
Settlers had to be deputized to tame the frontier, slave owners had to be armed to control the slaves, whites had to be armed to control the freed slaves, and as the US ramped up its imperialist adventurism the recruits had to be made comfortable with guns and inured to violence from the cradle to be effective troops. Kids who grow up with colonial occupation troops patrolling their streets and dodging bullets in the hallway at school become fucked up adults that volunteer to join the police or the army.
Then there's the effects of gun violence on society, which are all useful to the ruling class. Like Operation Gladio, gun rights act as part of a strategy of tension to make the population receptive to ever more heavily armed police and justify ever more repressive surveillance. Assassination attempts and school shootings become bloody shirts they can wave to get whatever they want.
Not that I am trying to downplay the need for an armed and militant workers' movement, I'm merely contextualizing it. Perhaps we can use the laws to our advantage, but we can't lose sight on why the law is the way it is.