I think the problem with NFL gaining popularity internationally is the complexity of the game. Looking from a non-americans point of view, the game is very complicated and hard to understand for the casual observer. There are a huge amount of laws and technical terms to understand which makes it really hard to get interested in the game because most of the time you have no idea of whats going on.
Whenever I've watched a game with anyone new to the sport, generally they are baffled by what is going on - they don't understand what a 'down' or an 'incomplete' is, why people appear to be tackling each other nowhere near where the ball is, why players start doing stupid dances after they make a tackle, and most importantly why after every play there's a break and after every turnover there's a bloody ad break!
For me personally, I only took an interest in the sport because I bought madden 05 a couple of years ago and I reckon it took me about a year to get a good understanding of the intricacies and nuances of the NFL. In saying that, having never played Football at an organised level and only ever watched about 10 full games my technical understanding is still pretty weak. Because of this I don't think the NFL will ever catch on internationally because to the uninitiated, it just takes too long to understand and is too boring to watch.
