Are you insinuating ... that Americans are unable to understand British English?
Maybe the American readers themselves are able to understand, but American publishers don't believe that. To the extent that British authors (no names, no pack drill, Stross, stop fidgeting) will Americanize their books themselves to avoid having them butchered when the publishers attempt the job themselves. Leaving us with only the pre-yanked version, reading a Brit writer's accurate description of London life - up until we thud into a Friday night take-out bag of fries.