It's a tough thing to do. I always look at it this way: If you took someone who's never even heard of hockey to an NHL game, you could spend 2-3 minutes giving them the basics and they'd have a great time.That's not to say it's tactically simple, you just don't need the details to have fun. What could you say about bike racing in 2 minutes? It took me years and years to get to where I could watch a race and really get whats going on and why. That's what you need to really enjoy it. I've shown friends and family videos like Pantani on Alpe d'huez or the 03 Tour stage to Luz Ardiden where Armstsrong got his bars tangled up. That's exciting stuff and they liked it, but for every day like that there's 4-5 230km flat stages that test even my devotion.
I hate to say it but I don't think bike racing will ever really catch on in North America. It's likely there will even be a dropoff if when LA retires no other US rider steps up.