Sorry StagN8 - that was meant to be a new sentence starting after U.S.
To clarify, both US and Europe are likely to use iris scanning for verification (IMHO). Users of the system (to begin with at least) will pay a $100 fee to be scanned and their details placed on a smartcard (like a credit card with a computer chip inside it). So at present it's mainly a way of avoiding queuing for immigration/passport checks (like the fast-track procedure at JFK/EWR).