Lance Armstrong stripped of tour de france titles

They don't really have conclusive evidence that he cheated, but they can show that over the course of many tests he had had blood transfusions, which is indicative of blood tampering. And most likely most or all of the other athletes are doing the same thing. I don't know that I would necessarily agree that they went after Armstrong because of some grudge between the US and France. It seems more likely that they would go after him because he's a prime target for making an example of. It's pretty much accepted as common knowledge that most/all of the athletes cheat, and that's an unfortunate fact in any sport. It leads to kids feeling like they have to do the same thing to be competitive in their sport, even if they have natural talent. Going after a target like Armstrong is a good first step to changing that, because he's idolized by many people and a number of those people will perhaps change their opinions or at least become passionate about the topic as a result.

Beyond that, the organization that is charging him probably needs to somehow justify their existence, and are also most likely attempting to get their name on the map. In other words, publicity.