If two thirds of the people voted to get rid of our constitution and go to a monarchy?

Our constitution allows that if the people of the US by two thirds of popular pupular vote. Decided to go back to a Monarchy which the gover ment would have to do. Then would we still have the right which we think we do to tell other countries how to run their lives. What right do we have, now wouldn't we fight if someone tried to tell us what we can and can't do.