There are web-order places in NA, it's just they're all mountain bike and road focused. Performancebike, nashbar, coloroadocyclist, ...
There are very few websites in NA that sell track stuff, and those that do have a very limited scope/brands. Ben's cycle is decent, and I can't think of anyone else off the top of my head. Business cycles was really good when it was around but the owner retired. Sadly, there actually used to be more track part availability 15+ years ago even though the sport was smaller then.