I was taught that language and culture are inseparable
They are, I assure you. A decade of studying minority languages has taught me this incredibly valuable insight. The thing is, you're talking about French, which like English, doesn't belong to one culture and hasn't for centuries. And one culture French belongs to is American (US) culture. I'm living proof of that, because I'm the daughter of someone who was born into and grew up in a part of the US where French has been spoken since it was a 18th century colony of an English king. And that Americans tend to kneejerkingly assume that languages other than English that have spoken here during the entirety of this country's existence--Spanish, French, German--as well as those that have been spoken here for multiple generations--Italian, Polish, Russian, various East Asian languages and many others--and even indigenous languages that managed to survive the settler genocide as all somehow "foreign" and not part of our culture shows a real deprivation in our own awareness of who we really are as Americans. That's in addition to the historical fact that the French and Americans have has a long-standing cultural relationship with each other that extends far back before our current age of global US media domination to this country's very origins. (I'm also living proof of this, as my surname comes from an officer who served in Lafayette's army that came over here as result Benjamin Franklin's successful ambassadorship to France.)
But back to the fact that French doesn't belong to one culture--this touches on something that bugs me to no end, and I deal with it a lot with English and Spanish too. It's the idea that a "world" language still only belongs to its country of origin, and that anyone speaking it outside of that country is speaking some bastardized version of it. As I often tell English folk who pout online about the dominance of US English, "If you wanted to maintain control of your language, you shouldn't have gone out, colonized half the planet and supplanted countless indigenous languages with English." And it chafes me the same way whenever I see similar shade thrown on varieties of French and Spanish that are spoken outside of France or Spain, because it's the same old story. A lot of people do this without realizing they are, because they are so conditioned to thinking this way. There's a lot of minds out there that need to be decolonized.
The point is, languages that have become a dominant or otherwise highly influential language in countries that were formerly colonized now belong to those people and their cultures, end of discussion. This means that with French, it belongs to North American culture, to Northwest African culture, to Vietnamese culture and to every other culture of all other former colonies of France around the world, not to mention to the international societies of academia, science, art, music and literature--not just to Europe. This isn't the same sort of thing as if we're talking about a minority languages whose language and culture has had very little influence or presence outside of its own community. In those cases, yes, that one language belongs to that one culture. But with "world" languages like French, the language easily belongs to many and you can very well study French without giving a damn about Europe or l'Hexagone. Honestly, I often find it better that way.