Good question. I dunno the answer to that one.
After a century of public schooling progressing to the vacuous socialism that is taught now and five decades of actively taught socialism and nihilism in the Universities the population has no spirit left, simply resigns itself to accept whatever the barbarians offer. All those hundreds of millions of guns are wasted resources if no one can use them when it becomes necessary to preserve civilization. We just stand by and let it all happen.
Good question. I dunno the answer to that one.
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There are many people, in fact the vast majority, who have always relied on law enforcement to protect them from harm, and who therefore lack the psychological mindset required to actually commit violence in defense of themselves and their family. Conversely, violent thugs readily take advantage of this weakness and attack their victims with impunity.