Do you believe that if a group of government officials swears to do everything they can to obstruct every lawful action of their CIC, even if it is something they have no real objection to, that it is not tantamount to insurrection?

And if they do this action simply to hamstring the President, to make him look bad, to appear helpless and powerless, to embarrass and humiliate him, to cause problems for the nation that can then be blamed on him so that he will be weakened and not elected again, or to simply discredit his party and political philosophy, that it is not tantamount to treason?

And if they continue these activities even after he is re-elected, in the hope that no one in his party will be able to succeed him legally, that is not the same as terrorism?

In a democracy one expects the loyal opposition to occasionally object to some actions of the other side, and do what they can to obstruct them. But when every single action and policy is opposed and frustrated, even those which in the past the opposition supported, that it is not clearly an attempt to throw the nation into chaos so they can assume power? That sure sounds like Civil War to me.

The Republicans have attempted to cancel the selection of a new Supreme Court Justice because they believe they can pick a more acceptable one themselves. They are not denying the President his choice by voting him down, which is their right, but which will be an action with political consequences. They simply expect him to not act at all, or to ignore him if he does. They may change their mind because of outrage by the American people, but the fact remains, they actually proposed this action, and if they think they can get away with it, they will still do it. This is not all that different from dissolving a parliament, or cancelling an election.
Its rebellion and insurrection, and the bloodshed will not be far behind. If they encounter determined resistance, they will have nothing to lose.

After all, the President they hate is going to be gone in less than a year, these actions are not aimed solely at him. They are aimed at everyone who voted for him or who supports him and his policies and philosophy.

I guess you could call it "regime change". We already know they believe they're entitled to do it to other countries, why shouldn't they believe they have the obligation to do it to us. They really do believe we are illegitimate, they actually believe they are taking THEIR country back from usurpers. They tell themselves that every day, and we'd better listen.