It does not undo the Constitution, it utilizes the provisions of Article V. The States can modify the Constitution by Amendment when the Federal Government cannot or will not act.
If Congress ignores or rejects the call from South Carolina, then the States can go around them and convene the Convention. Wait and watch for the typical "it will be a runaway Convention" every time a Convention of the States is brought up.
This is their second biggest fear. We the People exercise our power via the States and there is shit they can do about it besides attempt to declare Martial Law and show the entire World they are really a tyranny and not the democracy they claim.
This is yuge. 17 States have already called for a Convention via their Legislatures, this call from South Carolina to DC will open the door for other States. 34 are needed to ratify an Amendment, which would be binding on the federal government.
Now I know why the shills have been working so hard to bury past notables. So much coming out at once, and the tweet saying Governor signed was dated April 13th.