Unlike the Focus ST, which shares the same brand of ECU in both the North American and European cars, the North American Fiesta ST ECUs are manufactured by a different vendor. At least that's the way I understand it.
This of course has the possibility of slowing down the R&D of ECU tuning on the North American cars. It may be a non-issue. But, I just wanted to share the info.
Maybe someone with more direct knowledge will be able to shed some insight.