Future, more civilized, societies will one day study the ruins of America with bafflement. Like, what were they thinking? Was this what liberty was to them?
Routine traffic stops, or felony traffic stops? I've never heard of that happening for the former, although there may be a few examples out there, but it's far from the norm. But that is indeed normal for a felony traffic stop, like when pulling over a stolen car, or after chasing a suspect from the scene of a crime, or if the car waited a really long time to pull over, or if an outstanding warrant was found when they ran the plates.
However, let's assume that the government has ideologically came to the same conclusion you've made and drafted a new constitutional amendment which outlawed gun ownership. There are incredible practical issues with actually enforcing it. How do you expect to collect 300 million firearms[1]? What do you do with 300M firearms once you have them?
There are also high rate of illegal (and therefor untracked) gun ownership in gang controlled areas. How do you expect people to feel about being disarmed when they live in an area surrounded by violent, illegal gun owners who haven't been disarmed?
What about the people who are gun collectors? Who may have spent their entire lives tracking down and collecting antique guns? Who's personal wealth may be largely in gun assets? Does the government pay them for each gun? Who the hell is going to trust the government to set a fair price for these guns? How much would it cost to buy 300 million gun and all of the related accessories and ammunition?
I'm barely scratching the surface here and this is assuming that Congress has already passed a constitutional amendment! Banning guns in the United States will never happen, because before any of these practical implications become relevant a new amendment needs to be passed in order to override what our founding fathers and a lot of the country see as the second most important amendment.
[1] https://en.wikipedia.org/wiki/Estimated_number_of_guns_per_c...