Panama Declares War on Austria-Hungary
The Central American and Caribbean republics were officially pro-Ally.
Of course Panama and Cuba were treaty protectorates, and Haiti, the Dominican Republic and Nicaragua were de facto protectorates - so their declarations of war or severing of relations with Germany were less than fully free will.
In 1907 Roosevelt appointed George Washington Goethals as Chief Engineer of the Panama Canal. The building of the canal was completed in 1914, two years ahead of the target date of June 1, 1916. The canal was formally opened on August 15, 1914 with the passage of the cargo ship SS Ancon. Coincidentally, this was also the same month that fighting in World War I (the Great War) began in Europe. The advances in hygiene resulted in a relatively low death toll during the American construction; still, 5,609 workers died during this period (1904–1914). This brought the total death toll for the construction of the canal to around 27,500.
The Great War at PBS