Answer: The reason why the US has a large fighting force in Europe is because in World War I, on April 6, 1917, when the United States declared war against Germany, the nation had a standing army of 127,500 officers and soldiers. Once the war was declared they attempted to mobilize the troops very quickly. Then the fatigued British and French troops, who had been fighting since August 1914, sorely needed the relief offered by the American forces.
Explanation: General John Joseph "Black Jack" Pershing was designated the supreme commander of the American army in France, and the American Expeditionary Forces (AEF) were created, the date of that occured in May 1917.