And you think a few thousand AR-15s wielded by untrained, inexperienced, people who are at best poorly led could make any difference?
More like at least 10-20 million a large percentage of which are veterans and police as well as state and national guardsmen.
Our mostly untrained colonial Militias kept the US in the fight against the largest combined land and naval power in the world for 3 years.
Afghanistan and Vietnam also proved conclusively that this still works very effectively in the modern world where asymmetrical warfare used against standing professional military organizations can in the end win wars of attrition.
Right now we're watching a pip squeak army of mostly civilian volunteers and conscripts winning a war of attrition against the 2nd Most powerful military in the world using a combination of guerilla/insurgent tactics and a small standing professional army.
If it came down to it the US military would be facing a situation where every building was a fortress and every tree and bush or fencerow hiding a militiaman with a rifle.
All combined the US military would have a hard time fielding 200,000 combat soldiers even scraping the bottom of reserves and guards many of whom would refuse to fight in such a scenario.
Don't shit yourself believing the US military would be able to simply mow over the millions who would resist them and no, the USG is not going to use nukes on our own soil against Americans and very likely would not do so even against an invading army because of the long term consequences.
Moreover, civil war in the US would put all of our foreign enemies on the march and we'd have to reserve our nukes to counter any moves they made.