It's just harder to get good practice in the USA, so naturally our TDM teams wouldn't be as good.
Essentially, Europe is, for the most part, eveny densly populated, while the US on the other hand is not. It would be 1) Harder to get a good team together because of the scattered population and 2) It would be harder to play an enemy.
Just because you are the one reading it doesn't mean you're the only one. This is a public forum and many may not know the answer who are interested. No harm done.
europe is roughly the same size as the united states with twice the population. and much of that population is centered in central europe. when you have more people in an area, your connection has less distance to travel, therefore the average ping you have is lower.
look at the european internet tdm demos, the majority of the time, the pings are 30-35. whereas in america, its pretty common to see your average ping being 50-60.
when your used to lower pings, its easier to adapt to lan play. and sweden generally puts out many of the top teams and they have the best internet as stated by many.