Cheap little things should come from Korea/China (Barina things sell well cause they're cheap, if we can get Corsa's here for that price I'm plenty happy with that.)
Midsize and Large Sedans/Wagons should come from Europe (Astra, Insignia with space for 'HOT' OPC models) :P
4x4s would be interesting. SUVs could come from Asia or Europe with big, premium toorak tractors from US; Escalade anyone?
Maybe a people mover? Maybe a Zafira revival?
Trucks should come from the States (Chevys, GMCs, etc)
V8 Coupes should also come from the states (Entry level being Camaro, Premium being Corvette)