As the OP said, other countries look on with bemusement at people arguing with a straight face that an anecdote involving one gun owner shooting another gun owner after he'd killed three people with an assault weapon widely and legally available locally proves that a policy of encouraging universal gun ownership is better than alternatives. Not least because some of said countries have four orders of magnitude fewer per capita gun deaths

Sure, we get that changing US gun culture might be a bit more challenging than, say, the UK, where there weren't that many people with handguns to start off with when they were banned, and so it was particularly easy to convince even most criminals carrying wasn't worth the additional penalties. What we find bizarre is that someone buys an assault weapon in the sort of store that's ubiquitous in the US and nonexistent in other countries, walks into a mall with it because local regulations say there's no reason to apprehend somebody entering a mall with assault rifles until they've killed someone, and that event gets chalked up as a win for local gun policy because the casualties were in the single digits this time due to the rare use of a civilian gun against a mass shooter