The leftists are the problem my friend. The conservatives are the ones supporting the Republic and its values.
I started watching at the point the video started when I clicked on it. I don't know if the guy was a liberal Presbyterian or a conservative one, but Presbyterians during the Revolution would probably be extremely conservative, at least socially, based on modern American criteria. So I don't see the connection to this and the leftists.
It's an odd thing to be proud about in church-- Presbyterians being behind overthrowing governments. I don't know if it was true, but that is the historical picture he was painting. Presbyterians had been the religion behind the northern political power for a short time before King James took over, and then it became an internal component in the kingdom. I heard King James did not like the notes in the Geneva Bible because they were not friendly enough toward monarchy for his tastes. One might argue that Presbyterian government is similar to a republic, even if it is not strictly Biblical. My understanding is that the Presbyterians expanded the model of the city government of Geneva to a national church government.
Btw, I agree that the shift left among leftists is alarming. I just don't see the connection to what you shared.