That didn't work out so well last time it was tried.
You are confusing the Civil War with secession. The secession worked perfectly. The South formed a government and created a military in less than 2 months. The war was lost, which took 4 years, but the South proved how quickly and seamlessly a new government can formed around a few or many states.
People griping on the internet are so eager to claim it will be the French Revolution. There is another alternative. Want “levée en masse?” Stop paying taxes. Enact nullification. There are avenues to try before weapons, and they exist at the state level. We do that and the Feds will show their true intentions very quickly. Then there will be no choice between whether to fight or go back to sleep.