We've found a snazzy interactive map that shows the location of the plant at every American-built car and light truck is assembled, along with information on that plant's unionization or lack thereof.
The New York Times piece also lists the nation of origin for each vehicle's engine and transmission, and the overall effect is to provide tirade ammunition for both ends of the political spectrum. For example, if you know that unions (and the hand-wringin', gun-confiscatin', Kyoto-treaty-signin' parlor-pink liberals who enable them) have systematically destroyed everything that was once good and true about this country, you'll be able to point to the proof, right there for all to see! Likewise, if you have no doubt that the same oligarchs who rammed Taft-Hartley down our throats are out to crush the last vestiges of American labor dignity (their hands still red with the blood of Sacco and Vanzetti!), you'll see the truth on this map!
[New York Times, thanks to Franzouse for the tip]