A couple of points. Firstly, bringing mental illness into it doesn't help. People with mental illness are overwhelmingly he victims of violence, no the perpetrator, and the implication that they are a menace just makes people hide their mental illnesses.
Secondly, controlling guns from the Phillipines (or elsewhere) wouldn't be that hard, there's border controls for a reason. And while you can 3d print a gun, it's no small thing, not something you can do on the spur of the moment. Sure, without normal guns, the proportion of 3d printed guns (or otherwise homemade guns) used in crime will go up, the total number will drop.
Third, getting rid of the 2A is a noble goal, but unachievable. Taking small bites out of the gun industry is the way to go. Also, stop subsidising them, because obviously.
As an aside, "assault weapon" bans based on irrelevant criteria and banning certain guns based on name, not capability is stupid. Hell, some manufacturers, when one of their products gets banned in California, say, can make an almost identical gun which hasn't been banned yet and sell that.