Along the banks of the Mahoning River in the struggling Ohio steel town of Youngstown sits a once-abandoned furniture warehouse that has been converted into a sleek new laboratory. Inside is a Silicon Valley-style workspace complete with open meeting areas and colorful stools. Several 3-D printers hum in the background, while engineers type computer codes that tell the machines how to create objects by layering materials. The lab, called America Makes, is the first in a series of so-called “manufacturing innovation hubs” that President Barack Obama has launched with the promise that they could revitalize America’s industrial sector and spur...