When Chen Mingxu was a boy, U.S. businessmen poured into rural China, welcomed with tax breaks and steamed turtle. Thirty years later, in a kind of reverse migration, Chen finds himself in southwestern Alabama smiling wanly over bacon-wrapped meatloaf and banana pudding.

Chen, who employs about 200 locals, manages the first U.S. factory built by Golden Dragon Precise Copper Tube Group Inc. with a $120 million investment in Wilcox County, one of the poorest counties in Alabama. The state coughed up around $20 million, outbidding dozens of other cities and states hoping for the jobs and investments.

Last year, Chinese companies plowed $12 billion into the U.S., up from zero in the early 2000s, making it the fastest-growing source of foreign direct investment in the country. Chinese-affiliated companies now employ more than 80,000 Americans, according to New York-based Rhodium Group, which tracks cross-border investment.