American & Chinese Mahjong: Key Differences at a Glance

Winning Hands
Chinese: Fixed traditional patterns
American: Annual changing card 

Gameplay Style
Chinese: Organic, fluid strategy
American: Structured, card-driven strategy

Joker Tiles
Chinese: Not used (in most traditional rules)
American: Essential to gameplay

Pre-Game Play
Chinese: No Charleston
American: Charleston tile exchange phase

Annual Cost
Chinese: None
American: $15 NMJL Playing Card