The American forces had their uniforms with zippers and buttons that can easily be seen, so its somewhat easy to tell the difference Good thing she noticed it, that's one more German to interrogate......
To be fair, for all the opprobrium heaped on Hitler's decisions, Churchill was equally capable of demented decisions, as was Uncle Joe.
The facts are, running a modern war and state is too much for any individual; and politics always brings imaginative nutters with boundless unjustified self-belief ( vide Bonaparte ) to the helm.