The US has been providing similar help to the UK since the 1960s. There, the US provided the missles (first Polaris, then Trident) and their launch tubes, while

The US has been providing similar help to the UK since the 1960s. There, the US provided the missles (first Polaris, then Trident) and their launch tubes, while the UK built their own warheads and subs though I seem to recall the US's providing information (obtained from nuclear tests IIRC) important for warhead design and maybe nuclear material (i.e., plutonium).