America restricting others from accessing technology, like it is doing with Anthropic's Mythos/Fable, isn't unprecedented:

This is not the first time America has tried to restrict access to frontier technologies. After the second world war it stopped helping Britain’s nuclear-weapons programme. When modern cryptography emerged in the 1970s, it blocked exports, before accepting the trade-off between having secure allies and using secrets to boost its own offensive capabilities. Uncle Sam still refuses to share its best military equipment, even with close allies. America kept the f-22 fighter for itself; allies got the f-35.