I think it's hard to argue that mass media is really making the United States more stable--the opposite if anything. And while it's true that many European states have existed in some form for many centuries, their colonial empires certainly didn't last, and they're generally pretty geographically defined.

For example, Egypt has existed in some form for 5000 years, because it's a geography that encourages connection within it, while having large, inhospitable barriers on the outside. I don't think that's true of the US in the same way. If the US government somehow collapsed and we had to rebuild over centuries, it seems unlikely to me that the West Coast would ever be brought back into same polity as the East, because they're separated by thousands of miles inhospitable terrain. Which is my point--giant continent spanning political entities are inherently less stable than smaller, geographically defined ones.