Furthermore the Americans solved the 4-rotor problem (even harder), something the British were not able to do.
That's bullshit. The British knew exactly how to crack the four rotor problem: they needed bigger and faster bombes, but they didn't have the resources with which to build them. In fact, by using some tricks, they were able to have some success with the existing equipment, but a permanent solution was only arrived at when the USA joined the war. An agreement was reached to share cryptanalysis efforts and the Americans with their enormous resources and significant design input from the British were able to build the required bombes.