Wikipedia's list of national faux-pas is wonderful — though they don't have any entries for Canada. I guess we're just the easy-going sorts (though Canadians do get shirty over being mistaken for Americans, I suppose).
Germany
# In German business dealings, scooting your chair closer to the host is considered an insult. [65]# Flashing the American "OK" gesture is considered inappropriate because in Germany that gesture refers to the anus… [66]
United States of America
# It is customary to say, "I'm sorry." if you cause a person pain and/or suffering, unless this is done as an act of aggression or war.
(via Kottke)