I recently had a conversation with someone who said that he looked down on the goyish holidays like Thanksgiving because there are no obligations to the day. It's a day off, but you don't actually have to do anything as one would on Jewish holidays. There are no Halachic responsibilities to fulfill.
To an extent I understood what he was staying and I do appreciate that Jewish holidays are often more community-oriented and there are things that need to be done that add to the holiday aura. The hunt for top notch esrogim, while silly in one sense, does add to the festivities in some hard to define way. It just wouldn't be Succot if such hunting stories weren't shared.
But the fact is, Thanksgiving is full of traditions even if there are those individuals who don't partake. A big meal with the obvious traditional foods, different types of holiday decorations in the halls or on the lawn, and even to seriously sit down and count your blessings. In the same way that people compare the size of their turkeys I see people talking about the level of beauty in their esrogim or how late they finished their seder or how long their break was on Yom Kippur. Of course there are those that don't care for any of those things and simply do not involve themselves, but regardless of that these are aspects of the traditional holiday observance that still exist.
It is true that many Americans can go through Memorial Day with just a barbecue, if that. But some take it very seriously and may take a few hours of their day to visit a veterans' cemetery to show their respects and deep appreciation for the sacrifices of others for their sake. Some towns schedule whole events and parades and really make a big deal of it all.
So I think the differences are really relative. The person I spoke to just didn't see American customs as obligatory. On Jewish holidays there are things that need to be done a certain way or else the holiday is not properly fulfilled and for some serious-minded Americans it is exactly the same way.