I see what you are saying, but it is kind of the point. Socio-economic status plays a huge role in increases of not just gun violence but also suicide. Placing restrictions for the most vulnerable parts of the population to obtain them, while it doesn't seem desirable, can go a long way in reducing harm. In turn, funding from increased taxes that weathier individuals pay can be used to aid those same people by investing in mental health care.
https://luskin.ucla.edu/connection-poverty-inequality-firearm-violence
It will shift manufacturing desire. It will become cheaper to manufacture in Europe and ship to the US, costing jobs and tax dollars to the US economy. Otherwise, it will cause prices to increase in the US. You're dismissing it as non consequential, but that couldn't be further from the truth.