That's not correct. The US used to have an assault weapons ban, for example, but George Bush let the law lapse and the NRA made sure that even when Democrats retook the White House, they could not get ban through Congress again. The number of mass shootings began to skyrocket after than ban ended.
There used to be much more restrictions, background checks and waiting periods, but lots of states have gotten rid of those. The states that want more restrictions have been stymied by the Supreme Court.
Gun control works. But the US government in all branches is so corrupt and/or right-wing that getting new laws passed will be impossible for a long time, if ever.
Guns are a big reason (along with abortion) that a lot of Americans (including myself) think inevitably the country is going to break apart, as it did over slavery in the 19th century.