Almost all of these were accomplished by the individual states (not the feds) - and you would have to show me proof that they were mostly done under sponsorship of liberals.
I think you are in error. The federal government is responsible for nearly all of the improvements. Sometimes through mandates to the states.
And...if it is true, and I do not doubt it, that autos account for more deaths and injuries in our country than do firearms, why aren't they banned in part or in whole? Why bother banning the small stuff and ignore the big stuff?
In 2010, auto deaths, 32,887, gun deaths 30,470. Not a big difference. Less than 8%.
Auto deaths are decreasing. Gun deaths are increasing.
Why not try to do something about both?