I'm not sure you can just look at just total population and total land area. The pattern of development in Europe is very different. I just got back from Munich. You go 15 minutes outside the city and it's farmland! In the U.S., it's low-density suburbs for hours in every direction outside a major city.
Incidentally, I didn't get LTE service in the farmland between Munich and the airport. That would be quite unusual in the U.S.