Thanks for coming on here with an official explanation.
I hate to be the wet blanket here. I love that you guys are moving your printing services to America, but it's a little disappointing that they couldn't match the shape that had already been established. Squaring up the decks before each shuffle is a pain and still doesn't work nearly as well as just shuffling cards that are all the same size. But if that's what I have to do, then I guess that's what I have to do.
Just so we know what to expect, would the following be accurate?
Base box: larger Chinese cards
Character Add-On: some larger Chinese still available; smaller American going forward
Adventure Deck 1: larger
Adventure Deck 2: larger
Adventure Deck 3-6: smaller