Producing cars on two continents and shipping them both ways makes a heck of a lot of sense when you factor in the logistics of moving them from the point of manufacturing to the point of sale. If an auto manufacturer were to produce all their cars in Asia and ship a large number of them to the U.S., they would pay a higher shipping cost because the cost would have to include an empty return trip for a large ocean-going vessel.
A better scenario would be to produce a bunch of Model A vehicles in Asia, and a bunch of Model B vehicles in North America. A bunch of the Model A units from Asia would be transported for sale in North America, and a bunch of the Model B units from North America would be transported for sale in Asia on the same vessels that brought the Model A units from Asia.