Explain America's industrial growth during the World War I era.

American industrial capacity grew a great deal during the World War I era, so much so that it ended a recession that happened early during the Wilson administration. The United States exported goods to help Britain and France in their war against Germany. While Germany also had access to this assistance, it did not have the financial backing from American financiers to underwrite its loans for American war materiel.
Once the United States joined the war in 1917, government became heavily involved in the war industry. Government negotiated directly with labor in order to prevent the industrial strikes that were common before 1914. The federal government also placed orders for raw materials such as coal and metal in order to fuel Allied demand. Going to work in a war industry was considered patriotic. The war curtailed much unionist or otherwise leftist thought in the United States; this was especially true after the Bolshevik Revolution took Russia out of the war.
The abrupt end of the war saw the United States become the world's industrial leader as well as the world's leading creditor. World War I was instrumental in making the United States into a superpower.

While the U.S. economy was in a recession when World War I broke out in Europe in 1914, the economy quickly rebounded while the U.S. provided war materials to Europeans. The period of American neutrality, which lasted until 1917, allowed the U.S. to convert factories to wartime use so that they were already running when the U.S. later joined the war.
The American government bankrolled a lot of the new production. During the period 1914 to 1918, 3 million people were added to the military payroll, while one million people were added to the government payroll. Unemployment declined from 7.9 percent to 1.4 percent (see the National Bureau of Economic Research statistics at the link below), as people were employed in the military and in defense plants. The government also controlled prices and rates of production through agencies such as the War Industries Board. Much of the industrial growth during World War I was fueled by government spending and controlled through government administration.
https://www.nber.org/digest/jan05/w10580.html