> The US is less corrupt than France for example

Careful there. The Transparency International page you link to is the perception index.

It measures what a set of people perceives corruption to be like in each country, and composits results from a number of different surveys in a way that as far as I know is not benchmarked against other data to verify if survey results actually matches reality.

You can not use it as a measure of how corrupt a country actually is. It's likely that it's an indicator when the numbers are very far apart, or that it can be used to spot trends in a country over time, but the relatively small difference between France and the US seems unlikely to be sufficient to draw any conclusions.