Australia made it work. Europe makes it work.
Are you saying that they're more competent and effective than the US is? If not, why are they able to make it work but the US wouldn't be able to? If so, what parts of their governance make them more effective?
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Oh you silly billy.
The US still has those things, in addition to mass shootings.
It's not an "either or" here thing with the US, it's an "and also" thing.