SEOUL — Elon Musk’s Tesla faces strong new competition in the cutthroat American electric vehicle market with the opening of a Hyundai Motor “metaplant” in Georgia that’s gearing to eventually churn out half a million vehicles a year under its three corporate brands.

With the Georgia  governor, Brian Kemp, at his side, the chairman of Hyundai Motor, Chung Eui-sun, opened Hyundai’s “dedicated mass-production, electrified vehicle plant” near Savannah on the day that President Trump announced 25 percent tariffs on imported motor vehicles starting April 2. Mr. Chung and his aides took pains to deny the widespread impression the new plant was a tariff dodge.