> I also wonder how well even armed citizens can defend themselves against a tyrannical government in this era of militarized police, modern weapons, and SWAT teams.

Citizens have proven very capable of defending themselves in Iraq, Ukraine, Syria.

It's true that a government willing to firebomb entire cities and murder literally everyone could overcome that resistance. However, in the modern era a government that did that would quickly see the entire world turning against them.

It's also worth keeping in mind that even large, powerful, and well-armed militaries are only a fraction of the populace. In the US, something like 1/100 people are in the military. So if the US military turned against the population, and the population resisted, they'd have to fight a force that's potentially 100 times their number. Unless they were willing to firebomb their own cities and murder innocent civilians (as opposed to guerrilla fighters), they'd quickly be overcome.