Can ASDA be shorter than TORA?

Yes. At some airports—especially in the U.S.—ASDA is shorter than TORA due to land-use restrictions in the Runway Protection Zone (RPZ) beyond the runway. This area must be free of roads, buildings, or other obstructions to ensure safety in the event of an aborted takeoff.

See FAA Advisory Circular AC 150/5300-13A, Paragraph 310 for more on RPZ requirements.