I think the difference in the USA is that the people(we the people) are who are in charge and over the government and so the president(POTUS) is an servant (public servant) and the people "we the people" are the rulers over the servants. So yes if any of those public servants begin to act as if they are kings or dictators over us(we the people) then yes defiantly if they cross the path where they are overthrowing the "we the people" and becoming dictators or kings it is treason.
We have a different electoral system to the US, but the catch cry of most Aussies I have chatted politics with has been they wished the polies would remember they've been selected to serve the people and not their parties, nor their egos, and certainly not so they can line their pockets with the electors hard earned. I'd be telling a lie if I said most Aussies hold the politians in high esteem. Nonetheless, the politicians have been selected through our present electoral system, and we are obliged to recognise and honour that fact.
Quite frankly, I think Aussies would be up in arms en masse if any politician or political group dare try to remove our democratic freedoms. I suspect they would have a verve for protecting their hard earned democracy that would match US residents, if not more so.
But that's a highly unlikely scenario in any of the contemporary Western democracies. What is a more likely scenario is a deranged person getting hold of self loading weapons and creating carnage. There's no foolproof way to stop that happening, but there is certainly methods we could apply to mitigate against it, if we didn't allow our fear and self interest to overrule common sense. If however the threat is real and you feel you need to arm yourself with self loading weapons to adequately protect yourself and family from armed evildoers in your society, and it's legally ok to do that, then do it. But if it was me, after arming myself I would be quickly working on an exit strategy from that environment for me and my loved ones, post-haste.