There was a long period of time where there was basically no NA pro scene in Counter-Strike. This was during the CS:S era.
The game stayed popular with Europeans though. They kept playing, and thus never lost their edge.
With the rise of CS:GO, the NA scene is trying to scrape off years of rust while playing against well oiled machines.
To make things worse, NA is a huge place, making it a lot harder for teams to form and for teams to scrim against each other. Time zones and geography make things hard.
Meanwhile in Poland, five people can buy a house and live in it while they play CS. No problem.