Cupcai, there's a LOT of Americans who have no idea who Wayne Rainey is. Unfortunately, motorcycle racing just doesn't have that big of a following here in the states. Motorcycling period is only popular in certain areas of the country, most notibly California and the south, where you can ride year round. Harleys and more specifically custom choppers have glutted popular culture lately, with a bunch of custom chopper building shows like American Chopper taking over many cable channels. Buying a $40,000 custom is a fad that's starting to wear around the edges, and it's my belief that that bandwagn willcollapse under it's own weight pretty soon.
SBK, and I'm assuming you mean World Superbike is followed a little by some race fans here, but you are right, those that do follow motorcycle road racing mostly tune into AMA Superbike (aka the Mat Mladin show), Formula Extreme, Supersport and Superstock which is my favorite since that's where they race R1's like mine. That movie Faster has raised interest in MotoGP, and hopefully the USGP will go well enough that more Americans will see what they've been missing. For now, NASCAR is king, although with the advent of Danica Patrick, Indy is getting more attention lately. My dream is to see an F1 race. That'll have to wait till next year though, the wife won't go for two race vacations in one year!