In order for the telcos in North America to compete against the cable operators, the IPTV technology has to be really mature and be feature rich. You have in North America to offer HD and PVR if you want to compete against cable. Only now with the nextgen set top boxes is it possible for an operator in the US to offer HD and PVR and deliver the services over their bandwidth constrained ADSL networks. On the other hand, in rural America, cable is not as strong as the cable operators have not invested as much.
In Europe you do not have a strong cable presence. IP TV in Europe would sell even if it offered just SD and without VOD because cable operators are not so strong there.
Second reason for better IP TV penetration in Europe: In Europe many people live in urban areas. In urban areas the loop lengths of ADSL are shorter. In the recent times they were less than 5,000 feet in European cities. And over that with ADSL, you can offer 20+ megabit/sec to home and that is plenty for standard definition services.
Third reason for better IP TV penetration in Europe: Europe has more IP TV offerings than can be found in the US.
Fourth reason for better IP TV penetration in Europe: You have the financially more stable incumbent vendors like Siemens and Alcatel-Lucent focusing more on Europe. Of course their solutions were not around when Fastweb decided to do it alone with an in-house developed IP TV solution some five years back.