There are a couple of reasons we don't yet have American Samba.
As others have mentioned, it's considered a peripheral dance in the American style. And since the videos are very expensive and time-consuming to produce, we have to focus on the dances with the greatest demand first. American Samba is fairly low down on the list (following at least 5 or 6 other dances, including Hustle, Merengue, Nightclub 2-Step, Argentine Tango and even possibly Bossa Nova), but that's not to say it won't ever happen.
Another reason American Samba is not a priority is because there is so much overlap in the syllabus with it's international counterpart. The two Sambas share a good 90% of their syllabus patterns (and 100% of their technique) in common, so it's not a particularly wise use of resources for such redundancy. However, one idea that's been floated is to have Mark and Viola (our Int'l Samba dancers) fill in the remaining 5-10 American Samba patterns, which could be done very quickly and inexpensively. Then we could re-brand the overlapping patterns and call it a dance. Might work as an interim solution...
Regards,
Jonathan Atkinson
www.ballroomdancers.com