Remember that the world was much different in the first half of the century. I see a lot of projection of the current situation of U.S. dominance in technology that did not exist back then. Consider that it was a German chemist (Otto Hahn) that did the original work that discovered fission decay products (from Fermi’s work in Italy). And most students pursuing advanced degrees, especially in chemistry and chemical engineering took their degrees in German. The great chemical companies and processes were all German. And the Japanese were not a backwater either (nothing quite the stress of restricted access to oil and other scarce resources to make a resourceful people inventive).

p.s. The U.S. came very close to failing for a lack of German chemical engineering competence. We ended up destroying both of our uranium and plutonium production facilities in desperation just to scrape out and recover from the detrius the materials required for the first bombs (General Grove and the contractors took a few too many shortcuts and we were not capable of doing German-quality manufacturing of tools and tooling). Generation 2 of those same facilities took a few more years to come online. Which made the Soviet success a double shock.

But for the Grace of God…