Political map of North America & the Caribbean 06 April 1917 (United States Enters the Great War): While the US was embroiled in Latin America (Banana Wars), the Great War (World War I) had erupted across Europe, pitting the German-led Central Powers against France, Britain and Russia and their allies. At first the US was neutral, but gradually it came to see Germany as the greater threat. Germany's 1917 announcement of unrestricted submarine warfare in an attempt to starve Britain into surrender (U-boat Campaign (World War I)) further aggravated its relations with the US and, when German plans to incite a war between Mexico and the US (Zimmermann Telegram) were uncovered, America declared war (United States declaration of war on Germany (1917)).