Well, what they told you in license class is wrong. In fact, the French use MOX fuel in light water reactors. It is an admisture of normal uranium fuel and plutonium, using plutonium recovered from spent reactor fuel.
Comparing Europe to America is like comparing a duck to a fly.
To begin with, the population densities are completely different. The entire country of France is the size of Texas. Their People mostly live in shoe boxes stacked on top of each other.
Add to that, the fact that it is much easier to use public transit than drive in that country, and the roads are barely two bicycles wide, it’s easy to see why closely contained Nuclear Power works so well there.
Our biggest problem is, that we are too spread out for it to be practical. We would require many more plants because of all the expansive distances we have to move electricity.
It may have an advantage in highly urbanized cities on the East and West Coast, but the bulk of the population lives in fly-over country.