Worse than that, the Chain Home system was not particularly advanced even in 1939, the C3 system used everyday technology of the time. I believe the British were obliged to divulge how such things worked under the terms of Lend Lease, but even if it wasn't shown to the US it is a pretty simple thing to figure out, just needing a lot of effort getting it all working.But, crucially, the Chain Home system AND the critical C3 infrastructure were in place and thoroughly tested before the onset of war. Development of an integrated C3 infrastructure commenced in 1937 and US forces in Hawaii hadn't achieved even that by the end of 1941. Yes, the US wasn't at war when the Japanese attacked but neither was Britain when the Chain Home system was developed and integrated. It's still an incredible oversight by the US military not to have even a rudimentary radar and C3 infrastructure by the end of 1941 given the knowledge of what had already happened in Europe and during the Battle of Britain.