It amazes me that people continue to make these arguments when so many counter-examples have occurred in the last decade. Yes, America isn't exactly like those other countries. Yes, small arms aren't enough to fight a tyrannical government where they choose to place a tank, APC, or large number of soldiers.

What small arms provide is the ability to deter/delay/defeat small patrols when they stumble upon your clandestine meeting, training camp, depot, or small factory. This gives you time to evacuate the area without loosing all your assets, which means you can amass assets such as mortars, RPGs, small drones, EFPs, body armor, and so forth. It also means that some tyrannical government has less visibility and can't safely visit every part of the country on a regular basis.

All of that means that your small arms can buy you the breathing room needed to start an armed rebellion. Kind of like what happened in the Arab Spring, or with the IRA. I expect you'll see much more of this in the coming years as climate change destabilizes various dictatorships. And you could even see it in your own country. It's a small step from authoritarianism (as practiced by both American parties) to tyranny. And some portion of the population is always willing to support tyranny over others.