I've always wondered about that too. Especially since Alpha 1 was smaller, and thus would've been easier to port. I think there was a 32x version in development, but that doesn't count.
Apparently Alpha 1 was ported to the CPS Changer, a home version of their CPS1 hardware (Alpha being a CPS2 game). That makes the lack of a Genesis or SNES port all the more puzzling.
It was still alive in the west. It's not exactly outlandish to suggest a port for markets outside Japan. I mean, considering North America and Europe got their own special 16-bit "port" of Virtua Fighter 2 in 1996, it's not such a stretch to suggest a Genesis version of Street Fighter Alpha 2 around the same time. (The last Genesis game was released in 1998)