... von Braun understood very well that you need to flatter Americans outrageously if you are to get anywhere in the United States.
Flattery or not, the reality is that the pioneering work in liquid-fueled rocketry was done by an American, Robert Goddard, mostly in the 1920s, and that it was the foundational science upon which von Braun, Ley, et al. built the German V-2 program.
Goddard's work is documented, so, barring any actual and credible evidence from you that such science was the pure or largely unadulterated product of one of your preferred European national cultures, then I prefer to accept the reality rather than your prejudices.
Life should be led like a cavalry charge - Theodore Roosevelt