Well, let's not forget the famous Pig War of 1839. That's the one that started when an Englishman's pig was shot by a Yank (it was probably rooting in his garden) on San Juan Island (on the border of what are now British Columbia and Washington state). It had never been established just which sovereign nation actually owned the island, and both countries sent troops. The soldiers and warships spent a summer there without a shot being fired, and in the end a pfennig was tossed. The United States got the islands, and very pretty they are, too.