2 things: other countries don't have 2nd amendment in constitution, and US doesn't pretend to be the same as all the other countries.
Changes to the constitution can and do happen. And it's kind of beside the point anyway because a degree of gun control already exists in the US without being in conflict with the constitution.
> US doesn't pretend to be the same as all the other countries
Clearly. You're also the only one where this is such a problem.
The United States has more individual freedoms than most (if not all) countries. The downside of those freedoms is when individuals use their free will for evil purposes.
But it's usually phrased as "there's nothing we can do" and gun control wouldn't help, which is dishonest.