>The United States shall guarantee to every state in this union a republican form of government, and shall protect each of them against invasion; and on application of the legislature, or of the executive (when the legislature cannot be convened) against domestic violence.
Also, explain Napoleon who was Monarch over the Republic of France
Yes, our constitution guarantees that each state will be a republic, not a monarchy.
> Also, explain Napoleon who was Monarch over the Republic of France
The French state while Napoleon was emperor is known as the "First French Empire", which replaced the "First French Republic". Eventually, after both the Empire and the Old Regime were re-abolished in 1848, the resulting non-monarchical state was called the "Second French Republic". So your example actually supports my point.
Norway is a democracy and not a republic; Zimbabwe is a republic and a dictatorship; France is a republic and a democracy.