In the US, ‘Treason’ is specifically defined in the Constitution:
“Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court.”
The writers of the Constitution evidently wanted to avoid criminalizing political differences.
The US could have convicted the leaders of the Confederacy of treason, but chose not to do so for political reasons.
Nowadays, since we have not declared war against any country since 1945, it is pretty much impossible to convict anyone of treason. Merely declaring you house an independent republic and holing up with a couple of guns is not considered impressive enough to deserve being called ‘levying war’.
Charge everyone involved with the highest crime that exists for their circumstances. Send them to jail. Render them penniless. Shut down all the criminal elements instead of making excuses. That will wake up many and change public opinion.