Tesla cars aren't union made, but they are the most American-made

• Every year, Cars.com assembles a list of the most American-made vehicles. 
• Last year, Tesla only claimed the two top spots. Now it has the entire top four. 
• The supply-chain differences are an interesting quirk of union-made versus non-union-made tensions. 

Tesla may not have ads featuring American icons like the Wild West, bald eagle, or stars-and-stripes galore, but it's still the most American car brand, at least based on its manufacturing.