Here’s what British people thought about 1970s American cars, which is still how they view most American cars today.
The issue is that American luxury cars until the 1980s were physically too big for European streets, given that they were constructed much earlier than American roads. When American luxury cars did finally downsize, you ended up with stuff like the Cadillac Cimarron, which nearly killed Cadillac for good.
You’d need better and more effective downsizing. Perhaps a longer and worse late 1950s recession leads to a greater sale for the Corvair (butterfly away Nader as well).
By this point, the Americans are much more accustomed to good small cars, allowing them to have a stronger basis for entering the European market. Lincoln and Cadillac should follow.
Another option would be to have the European luxury car industry of Rover and Mercedes-Benz collapse. If Europe is in a much worse place post-war (especially in Britain/Germany/Italy), the Americans will need to serve as the backbone of the car industry.