Having grown up in California, we thought the same for European wines. Why bother when they are no better than the local swill. Though I'm not sure how true your conjecture is as my family was in Amsterdam a few years ago and eating at a fancy french restaurant got talking to the sommelier and mentioned we now lived in Oregon which turned in to a conversation about Pinot Noirs of the Willamette valley. He knew all about them...

But more to the point, all the top french Champagne producers have large holdings and production in and around Napa. They probably care...