You need to look at real world examples in order to draw reasonable scenarios and conclusions.
After Kaddhafi gave the order to his army to fire on Libyans, 75% of the army deserted and returned to their provinces to protect their families. On their way home, they emptied out the armories.
What remained were officers in Kaddhafi’s elite guard and raw recruits with few weapons. They were completely incapable of carrying out any effective military operation. Many of the officers left the recruits to fend for themselves, and they headed for the Niger border, loaded with stolen loot. Kaddhafi had to order out his southern mercenaries in an effort to quell the Libyan revolt. When his mercenaries opened fire on students at a university, all hell broke loose.
The army deserters teamed with provincial militias and attacked the Kaddhafi dictatorship and his mercenaries. The mercenaries were executed and hanged from lampposts. Their towns were burned to the ground. The militias organized patrols to track down and capture Kaddhafi loyalists. The chief of the army was dragged into a courtyard and executed, as were other army officers loyal to Kaddhafi.
Khaddiafi himself was snared by a desert patrol and executed on the hood of an SUV with his gold-plated Browning. Here’s a picture of it:
http://www.theatlanticwire.com/global/2011/10/qaddafis-love-affair-golden-guns/43938/
True enough. But while we might eventually get some or even a lot of desertions from American military if ordered to attack American civilians, that is going to be little comfort to the first few people who fight back.
THEY will be dead, or possibly in custody.