It has been said in the US that the European Tour is about as strong as the Nationwide Tour, which would explain why the US team is favorite every time. However, those who say that were completely missing the point and the Ryder Cup proves it again and again.
First off, the European Tour pays very little money compared to the level of skill you need to win there. So if you want to make a decent living off the European Tour, you have to play much better than on the US Tour. Second, many European players play both tours or even mainly the PGA Tour. The days when the European Ryder Cup squad came from the European Tour and consisted of players, who had never played against the Americans before, are long over.
Looking at the world rankings, which are comprised from all tours, we find that the European squad is actually ranked better than the US squad. Let's square off the top 9 players on each side (the stats don't change, if we bring in all 12):
Team USA
#1 Woods
#2 Mickelson
#3 Furyk
#15 diMarco
#16 Toms
#22 Campbell
#23 Cink
#37 Verplank
#42 Johnson
Team Europe
#8 Garcia
#9 Donald
#11 Stenson
#13 Howell
#14 Montgomery
#17 Casey
#18 Harrington
#19 Olazabal
#24 Clarke
Just from the world rankings, this makes it 6-3 to Europe. And if the big 3 from the US team don't perform, it becomes a rout.
So, it's as easy as that: the Europeans win, because they are better players.
Ulrich