What if there was a forced secession of the liberal socialist ‘aggressive’ strongholds. I think U.S. would have most of the military on its side since a china-compromised Biden would make the U.S. and the military both vulnerable to its enemies, and for the military to back a false-president-in-china's-back-pocket would be unwise of them, and I'm sure they can see this (unless the military higher-ups are also china-compromised). They on the left have demonstrated quite clearly they have no regard for laws, just look how many they broke and still their electors were seated, so any of their protests that attempt to cite or mention laws are rendered null and void. You can't on one hand break law after law, and then on the other hand seek out the law for your protection.
As long as those forcibly seceded areas leave the U.S. alone, the U.S. would not be their enemy. Since the U.S. should have the support of the bulk of the military, it would be bad if they resisted their ouster.
Trump would stay in office because he won, and also because he clearly has overwhelming support.
Those that perpetrated the fraud, foreign and domestic, would be sought out much like the Israeli's did against the Nazi’s after WWII, and brought to justice (some for treason). Let them go live in china for protection from apprehension / trial.
In your scenario, such socialistic “seceded” states would seek out the aid of the enemies of the USA, just as they’ve been doing up until this point, but this time militarily. That of course would not be a civil war resulting from that.
Sorry, but the very premise of your question is severely flawed.
Who would "force the secession?"
If (and that's a very big "if") that "who" had that power - then they wouldn't need or want to excise any part of the country - instead, they would subjugate it.
Regards,