The fertile soil of American manufacturing has attracted billions in foreign investment over the past decade, promising to revive industrial heartlands from Michigan to Georgia. Like any garden, however, this economic renaissance requires careful tending—and sometimes the removal of weeds that threaten to choke out legitimate growth. Here’s the thing about these grand promises of foreign partnership: they sound wonderful until you dig beneath the surface and discover what’s actually growing there. The Hyundai Motor Group facility in Ellabell, Georgia, stretches across 3,000 acres of what was once sleepy farmland twenty miles outside Savannah. This $4.3 to $7.6 billion joint...