I would say that 1789 marked a turning point in the political history of both the United States and France. However, the turning point for the United States led to stability while the turning point for France led to chaos that would last for a number of years before finally resolving itself.
In 1789, the Constitution of the United States went into effect. This was a huge turning point for the US. Before this, the US had had a lot of trouble because it did not have enough of a central authority. Its states had too much power and this led to instability. The new Constitution fixed that.
By contrast, France became less stable in 1789. The start of the French Revolution overthrew the monarchy, which is a good thing. But France would face decades of hard times before it settled on a new form of government that would give it internal stability and external peace.