There are tons of great players near the top of the solo queue ladder that aren't on professional teams; just because they aren't well known does not mean they aren't as good or better than the professional players.
That's why surprisingly few of the most well-known professional players are even close to challenger (Dyrus, Oddone, XSpecial, St.Vicious, Chauster...). The simple fact is that there are a lot of really, really good players out there; most of the pros simply have been near the top of the ladder since season 1, and as such have established connections and a reputation, and are considered "known quantities" under pressure.
It would not in the least surprise me if the top five non-professional solo queue ladder players beat the NA All-Star team head to head.
In all honesty most of the professional players aren't really THAT good...what they are is flexible. They can play at a high level with a large number of champions (this is excluding the pros who are simply really amazing players, like WildTurtle or Sneaky) but aren't necessarily better than many other players are given their best champion (in part because they have to be flexible with their champion picks, and so don't get as many chances to practice their "main" champions). I don't think its a surprise at all that Cloud9 is doing as well as they are because if you look at the ladder ratings literally all of their players are in the top 50 on the North American server. The reality is that the practice those players get in solo queue is a much higher level than the practice that players like Dyrus or Oddone get, being mid Diamond 1 (for reference, that means that Dyrus and Oddone get to practice with me whereas Cloud9 players get to practice with Pobelter, Ecco, Megazero, and so forth).
Many if not all of the established professionals were at one time either the best or among the best at their position; but if you do not stay diligent you will not remain the best for very long. This is why I think that Doublelift, once the undisputed best AD Carry in North America and possibly the world, is the third best AD at best right now, behind WildTurtle and Sneaky. Mechanically he is still the LoL version of jesus but his game sense and awareness have always been lacking, and people are starting to be able to exploit that more and more as the game has opened up and become a lot more versatile.
In other words I doubt that the NA All-Star team for Season 4 (if there is one) will have any of the same players on it that were on it this year (unless the fans vote in someone who does not deserve to be there). I think this is the other reason that the North American teams don't do well internationally: they are known, predictable, and not even necessarily the best that NA has to offer talent wise.