Availability might be the biggest limitation. I know Wal-Mart, K-Mart, and I believe Target don't sell Naruto cards, thanks to some time ago (and they have yet to go back and say "okay, that's over, let's make some more MONEY!"; they just like MtG and PKMN, for the most part), which leaves places like where I live limited to the rare collector/comic store (Dragon's Den, 1.5 hours away, for instance) and the Internet (TnT, for instance) as the only good sources to get card packs or singles, and this lack of availability could make finding anything more organized than you and some buddies in your basement, or a part of your local gaming group's group playing for fun a bit tricky, again, depending on where you live.
In bigger places, of course, you can still find both new cards and events, so it could still work out for you.
I think Naruto has done okay over here, but I feel that they could have done better if the CCG, toys, and collectibles were ever a bigger thing in the U.S. Wal-Mart sells Power Rangers, and did sell DBZ toys during the last millennium; it's sort of a shame Naruto never got much for that.