Greece today. Portugal tomorrow. Des Moines ???
Politically, this could be a boost to fiscal conservatives in November. A bankrupt Greece, fighting on the streets between the fascists and communists, etc., will not play well with voters. Austerity is going to sell a lot better than more left-wing stimulus.
The great plains area of north america will be the last to suffer. East and west coasts will be the first, followed by the gulf, southwest, and the great lakes areas.