Based on what I've heard about CX, I can see how it would be a shock for a lot of Yanks. Things are pretty laid back at the training departments of most regional airlines, and the pilots in the majors know they'd have to screw up pretty badly to have it marked against them. I can't see a company as diverse as CX having a huge problem with colonials in general, but I don't have a hard time thinking of American pilots who would have a problem with CX trainers.
I consider my current company excellent training for CX: The new hire process is mind-boggling, the training department is absolutely draconian, management has a personal vendetta against the pilot community, and the command upgrade classes expect you to be able to assemble the aircraft from scratch. We've also got some of the most competent, close-knit crews to be found in the regional airlines and lots of interesting flying.