Change to Easy Mode in mod menu if you cant handle the difficulty. No tax on provinces gives a lot of benefits.

that means you expanded a lot and a couple of those provinces are -75 control
each such province gives -1 control factionwide
abandon or stabilize some of them to get rid of the chain rebellions
I explained this to another user who were gonna abandon their campaign and they returned with feedback that it took them only 10 turns to stabilize and they still didn't even build their landmarks / research technology that gives control factionwide
it varies from faction to faction but base issue tend to be the same