Republican government had already come to America. The confederated states had republican governments before the Constitution. From Ryan McMaken at mises.org:
One of the many myths that schoolchildren are taught in the name of American exceptionalism is the idea that the Americans finally embraced a republican form of government at the Constitutional Convention in 1787. This, we are told, was revolutionary.
The usual narrative goes something like this: In ancient times, the world saw the rise of republics in Italy and Greece. The Roman Republic was notable for its virtue and its status as a government of the people. But the Roman Republic, like the small Greek republics, was but short lived and was destroyed by the temptations of empire and despotism.
But then came the so-called American experiment. This new, noble experiment sprang up when America’s great men met at Philadelphia in 1787 to hand down to Americans a new republic—something revolutionary and innovative in the face of a world ruled by crowned heads.
This story is often accompanied by a well-worn anecdote about Benjamin Franklin. It usually goes like this:
Philadelphia, 1787. The delegates to the Constitutional Convention are just leaving Independence Hall, having decided on the general structure for the new United States. A crowd had gathered on the steps of Independence Hall, eager to hear the news. A sturdy old woman (sometimes referred to as “an anxious lady”), wearing a shawl, approached Benjamin Franklin and asked him, “well, Doctor, what do we have, a republic or a monarchy?” Franklin replied sagely, “a republic, if you can keep it.”
Most of my readers will surely have heard this little anecdote many times. The subtext here is that the United States had invented something altogether new with the constitution of 1787. The story suggests that in the late 1780s, Americans were not yet sure if they had the fortitude for a republic or if they would return to being a monarchy. Fortunately, the sagacious Founding Fathers decided “we” would be republicans after all.1