Actually, aerodynamic analysis of automotive designs predated Ledwinka's Tatras. Amos Northup tested his 1933 Reo Royale in a wind tunnel for drag and stability factors, and more notably, Chrysler did extensive and elaborate aerodynamic analysis of its 1934 Airflow, even going to the extreme of fitting ultra-slick nose pieces on its production prototypes to explore aerodynamics even more deeply. Rumpler and Voisin, in the teens and twenties, were tinkering with the aerodynamics of their designs, too, to a less significant degree of success, though.
1933 Reo Royale:
1934 Chrysler Airflow:
There are myriad examples of automotive designers and engineers exploring the science of aerodynamics that predate the Tatra. Another very notable example is John Tjaarda's famous streamliner concept car that he sold to Ford Motor Company after it created a sensation at the 1933 Century of Progress World's Fair in Chicago. Edsel Ford took this design, adapted it to front-engined configuration instead of its original rear-engine layout, and produced the landmark Lincoln Zephyr of 1936, which was the first really successful mass-produced "aero" car. Ferdinand Porsche traveled to America in 1933 specifically to study this futuristic prototype, btw. The influence Tjaarda's design exerted on Porsche's eventual VW Beetle is pretty obvious:
The Tjaarda World's Fair concept car:
The car it begat, the Lincoln Zephyr: