The infrastructure for a national strike does not exist in America. You need a lot of labor to be organized, and it just isn’t. We can barely get individual facilities to go on strike, let alone an entire country. We used to, and that’s how we pressured politicians into the New Deal, but organized labor has been dismantled since then.
As for why we’re not more like the French, a lot of it comes down to this: They have more unionized workers, as a fraction of the working population, than we do.
Perhaps we forget, here on our islands of leftist beliefs, but the average American is not a radical Socialist, Communist, or Anarchist. They are not tuned-in closely to politics, they are not media literate, they are not part of any active organization besides maybe a local church. They’re not going to upend their lives over something they don’t understand, without any way to plan with their coworkers.