I realized after I wrote that, that if your local North American airport is a major international gateway like ORD, the number of European cities you can fly to in two stops maximum is probably huge. But I was thinking of cases where you would always have to make one stop to get to an international airport from a regional one, hence my use of DSM in the example. The specification should be revised to read something like, maximum of two North American stops with the transatlantic leg being non-stop. Or to put it another way, I'm looking for tickets from North America to any major European international airport, not "any European city."