Yes, I agree those factors probably contribute to the fact that the US experiences far more school shootings than any other country in the world, but again while far more infrequent, there still have been school shootings in Canada, Australia, Europe, and many other places.
Keep in mind that I’m playing devil’s advocate here, but if we were to fix the things you mentioned: toxic masculinity is erased from the public consciousness and the government gives free mental health support to everyone, can you guarantee on your life that a school shooting would never ever happen again for any reason? Simple yes or no answer to satisfy Mr. Vance.
Oh hey look, we have the real world Firecracker!