The purpose of an armed resistance isn't a direct confrontation with an armed force. It's the death of a thousand logistical cuts. It's bleeding the country's economy dry by disrupting the commerce required to keep daily life running smoothly and crippling the regime's forces by making people afraid to sign up - one way or another. Whether that's neighborhoods chasing ICE out or people finding out where cops and soldiers live and "paying them a visit" in the dead of night. An armed resistance's goal is to simply be too big of a thorn to ignore but too entrenched and evasive to be worth the amount of money and effort it would take to catch them. Even just their existence in the media is a form of warfare. By simply being in the news they show a population that the regime can be resisted, even by just a bunch of people with guns.

Look at Napoleon's war in Russia in 1812 and his massive losses due to poor supply lines, disease, and the Russians scorched earth policy ahead of the fierce Russian winter. Or to the American Revolution, where a bunch of farmers with guns and the financial backing of France became such a thorn in the side of the British Empire that they became one of the most powerful and obnoxious countries of the past two centuries and are the subject that started this whole conversation.

You can turn your guns on the entire country's population, but then what? You're going to have a hard time keeping troops loyal when it's their friends and family on the other side of the gun, and terrorizing the population like that will make it impossible to keep the propaganda machine going. You'd be forced to rule through direct oppression, which would breed more resentment and more people willing to pick up a gun and fight back. Your only hope is to convince the discontent population that opposition is pointless and the true believers that you are right.