There are many newer fans here, myself included, and most of them seem like genuine fans. There are only a few I can think of that probably aren't and most of them are glaringly obvious about it. A good way to tell who the glory supporters are is how they act when we lose.
I also think it's to be expected that clubs get new fans when they are successful, especially abroad. Realistically, what are the odds that an American (or any foreigner) would start to support a non-successful club that probably doesn't even get TV coverage here over Barca, Real, Man Utd, Chelsea, Arsenal, Inter, Milan, etc. unless they have some special connection to a foreign city with a lesser club? Yeah some are glory hunters, of course, but not all new fans are. Everyone has to start somewhere.
But I'm also not one to call people out on it and I don't see the point, I don't see why people care so much, just let them all have their fun