I think one of the things you are overlooking is that there is a line here that is FAR different from that of Europe or the UK when it comes to dealing with the government.
You've cited the Civil War in several instances, but have neglected the fact that it wasn't total defeat that halted it, it was the offering of honorable terms on the field of battle by Grant that persuaded Southern leaders to give up the fight. If that hadn't occured, it is far more likely that the South would have fielded sizeable armies for several more years and the general conflict would have degenerated into a protracted guerilla contest.
The demographic of a North American civil war in the 21st century is light years from the original Civil War and of someplace like Iraq or Afghanistan for that matter. Swaths of territory equal in size to decent countries would go independant and those swaths not only would control a lot of food production, they would control most all of the logistical lines and sources for materials and fuels that the areas one would expect the government to rely on would absolutely have to have to continue an armed conflict.
As has been pointed out earlier, the educational, material and motivational advantages that the antigovernment forces would have over the government forces would be huge. I'd be willing to bet that greater than 50% of the workforces in not only heavy armaments, but especially in small arms, would walk off the job if they were supposed to be cranking out guns for pro tyranny forces. On the flip side, every Tom, Dick and Harry with a workbench CNC mill would be cranking out weapons and really good ones at that.
Your arguements best case scenario in North America would end up like a Zimbabwe but with nearly 75-80% of the able bodied population either armed, or with ready access to arms. Under those circumstances, the Zimbabwe situation wouldn't last very long...
Well, of course if you phrase the question ‘would you be against a tyrannical government?’ Then people are going to say ‘yes’ but it isn’t going to be that black and white. A government would need a ‘casus beli’ in order to take away freedoms, and some people will support that casus beli, just as they did when the suspended habeus corpus, introduced conscription and deployed troops on the streets of New York in 1863 (as well as fundamentally altering the balance of power over state goverments in favour of the federal government) which are the kind of things you seem to believe would cause the entire population of the US to rise as one against the government....