Dennis Crouch has just published a very interesting case note on Ford Global Technologies v. ITC (Fed. Cir. 2008). This is an appeal from a decision of the International Trade Commission upon an application by the Ford Motor Company to bar the importation into the USA motor vehicle spare parts from Taiwan. There is no system of design registration in the USA. Nor is there any kind of unregistered design protection except, curiously, boat hulls pursuant to Title V of the Digital Millennium, Copyright Act. Designs are protected in the USA by a special type of patent known as a "design patent".
Dennis's article suggests that the right conferred by a design patent has very little use in the motor vehicle after market except where there has been slavish copying and there are all sorts of problems over novelty. It is the opposite of the way we used to protect component designs with copyright (see British Leyland Motor Corp and others v Armstrong Patents Company Ltd and others  UKHL 7 (27 February 1986).
Competition appears to have been the big unspoken issue in Ford as it was in British Leyland. The position of the ITC seems to be closer to that of the the ECJ in AB Volvo v Erik Veng (UK) Ltd  ECR 6211 that to the House of Lords in British Leyland.