it depends on if its only a cosmetic part.
the lights might be a different shade, or look totally different. like a 92-94 sentra, where the japan ones stick out the side, and are clear housing headlights, or 90-93 integra, with one piece vs. three piece headlights., or it might be a totally different front end that never existed in the us, like 89-94 240sx/silvia, or 94-00 integra, which looks totally different.

for parts beyond that, such as engine parts. if you go with a jdm part, it might be made more performance orientated, but still be a part with factory reliability, unlike going aftermarket. sure the gains might not be as high with going with say jdm type r cams, as opposed to skunk 2, but its alot cheaper also.

now, for non factory parts, the best way to put it to a domsetic person would be, "would you buy a japanese cam for your camaro?" probably not. you would want an american part, where the cars main production and research exists. same deal, just a polar opposite. i would usually without exception buy parts from the people that have the most knowledge, and experience with the particular car im dealing with.

now for stuff like a/c controls and crap like that, it just looks different, and seperates your car from every other civic/240sx/integra on american streets, and makes it a little closer to the way the car was intended to be from the factory.