Also the US 90mm was no slouch. I remember watching a show on discovery channel a few years back, on how back in 1945, it was slaved to a radar and an experimental ballistics computer and could actually automatically track and hit on the first couple of salvo's low and middle flying aircraft.
That was the SCR-584 system, which included a radar and a ballistics computer. However it was not experimental and was comnpleted in mid 1943 and first deployed at Anzio. When combined with the US 90mm gun and VT ammunition it was state of the art: The SCR-584 Radar Tribute Page de KA9MVA
IIRC, it was also used with the UK 3.7in AA gun to help defeat the V-1.
The SCR-584 was one of 3 centimetric radar Gun Laying systems that were developed by the Allied during WW2; SCR-584 was also known at GL-3A (A for American) and there was also GL-3B (B for British) and GL-3C (C for Canadian). The GL-3C was actually ready first, but war priority and engineering problems delayed its introduction. [5.0] Microwave Radar At War (2)
There was actually more than 3 centimetric systemed developed, of course, but GL-3, A, B and C were developed to a common spec.
Video showing 75mmm Antiaircraft Vickers gun of the pre-war period, it was used in the WW2 by Romania and Japan. Note the calculator for setting the time fuze.