Make the PoD that the French never give up their rights to a Panama Canal to the USA. In the USA, President Teddy working under the Monroe Doctrine and Roosevelt Corrollary decides a French canal in Panama is unacceptable! He ramrods through Congress that a canal be built in Nicaragua. Canal zone given (seized?) in Nicaragua and Costa Rican borders (hey, keeps them safer from each other right? It's an international public service! Peace in Central America brought to you by American Imperialism! Thank you, Teddy.) And so you have a Nicaraguan canal and possibly a Panama Canal if the French actually go ahead and Colombia lets them. Panama may not exist as an independent nation. And you have the possibility that once Bismark is out of Germany and Caprivi is in that France sells to Germany the rights to a canal and you have a German canal in Colombia/Panama which causes the USA to seize it during World War I. If it is French then World War II takes care of that, the British/Free French and then the USA after December 1941 administer the canal, in the 1950s or 1960s Colombia nationalizes it.