“The most significant car in history”. It’s kind of an open ended statement. Depends how you want to interpret it.
As previously stated, the Model T appears to be an obvious answer. Not only did it shape the American landscape, but North American manufacturing as well. A close second and much more recognizable by its silhouette would be the VW Beetle, even though its heritage is more than suspect. However, it outlived the Model T in years of production and exceeded it in sales.
From a notoriety point of view, I’d have to go with lead photo - JFK’s Lincoln. But that gives away my age and its significance will so diminish once The Quiet Generation, Boomers and Gen X’ers fade away from existence.
The Lunar rover. It was a blip.
Then there were the franchise cars: Barris’ Batmobile, The Bandit’s Trans Am, and The Duke Boys and their ‘69 Charger. We all dreamed of owning, driving or being near one. Again, their significance will will diminish with the generations that loved them.
So I’m going with this:
It was invaluable to American GI’s in WWII and the Korean War and its spawn still roam the roads today. It’s an Icon that refuses to die or ride off into the sunset.