TLDR: Banning guns sounds easy, but you can't enforce it without trashing the other rights.

So, you ban guns.

There are over 400 million in circulation. These guns can last (effectively) over 100 years and people can make and do make them at home.

They also share how to make them with each other and that's protected under the 1st Amendment.

So, are you just going to leave 400 million guns out there with over 1/3 of the population who don't particularly care about gun laws?

No, you're going to have to go get them.

And then you're going to want to prosecute these people.

So, first you have to stop them from sharing information about guns, how to avoid getting caught, how to make guns, and how to hide them plus how to organize a resistance--violent or political--and that means chucking the right to free speech and privacy.

You're going to have to go into these people's homes and places of business to collect these guns.

There's no way in hell you're getting past all of the judges requiring definitive evidence to grant a warrant. There goes warrantless searches.

Oh, and once you have these people in hand, putting them in front of a jury to convict them when the odds are a good chunk of the jury isn't going to find them guilty is a massive waste of time, effort, and good will.

Beyond the fact you need at least 6 jurors typically and trying 100 million people for possession would require either career jury members or about 600 million people in a country with less than half of that in adults and--without knowing who is who--you're at risk of massive jury nullification.

Oh, and by convicting 1/3 of the population, who's going to grow the food and pay the taxes for the massive amount of new prisons?

You're probably going to need to bring back slavery to allow you to force them to grow food while in prison.

Finally, you can't take any new votes.

Once you piss off and alienate that many people, you're going to have an uphill battle every step of the way after that and it puts so many political hijinks on deck for the rest of the country's existence.

Imagine just losing enough of an election once to have people try to overturn such a policy?

Even if you stepped in militarily again, you start looking like Liberia in modern times: All the trappings of a good government and coup after coup with mock elections.