Introduce Canada and Mexico as border countries

Canada
http://memory.loc.gov/cgi-bin/query/r?ammem/gmd:@field(NUMBER+@band(g3400+ct001560))

Mexico
http://memory.loc.gov/cgi-bin/query/r?ammem/gmd:@field(NUMBER+@band(g4410+ct000472))

Carte du Mexique
http://memory.loc.gov/cgi-bin/query/r?ammem/gmd:@field(NUMBER+@band(g4411p+cws00187))

Map of the United States of North America with parts of the adjacent countries / by David H. Burr (late topographer to the Post Office) geographer to the House of Representatives of the U.S.
http://memory.loc.gov/cgi-bin/query/r?ammem/gmd:@field(NUMBER+@band(g3700+rr000060))

Central America, the West Indies South America and portions of the United States and Mexico
http://memory.loc.gov/cgi-bin/query/r?ammem/gmd:@field(NUMBER+@band(g3301p+ct000852))