Just as a point of reference: when I was in my high school years, I went on a student exchange. Before leaving, I made friends with someone else in the same program and we exchanged a number of letters.
Now, I lived in Sault Ste Marie, Ontario; she was in Traverse City, Michigan. You can
drive the distance in about three hours. Our letters usually took around ten days to make the trip, and sometimes as long as fourteen.
Now, the time to leave comes. I go to
Maebashi, Gunma-ken, Japan, and (IIRC) she goes to
Nice, France. Our letters go from spending two weeks or so in transit to arriving in
five days, like clockwork, every time.
Just goes to show you where in the world our North American postal systems rank, I guess. =)