After having a large part of their air forces shot out of the sky by ZSU 57, the US decided to fill their own gap in the SPAAG field:
"In February 1982 the prototype was demonstrated for a group of US and British officers at Fort Bliss, along with members of Congress and other VIPs. When the computer was activated, it immediately started aiming the guns at the review stands, causing several minor injuries as members of the group jumped for cover. Technicians worked on the problem, and the system was restarted. This time it started shooting towards the target, but fired into the ground 300 m in front of the tank. In spite of several attempts to get it working properly, the vehicle never successfully engaged the sample targets. A Ford manager claimed that the problems were due to the vehicle being washed for the demonstration and fouling the electronics.In a report on the test, Easterbrook jokingly wondered if it ever rained in central Europe."
ttps://en.wikipedia.org/wiki/M247_Sergeant_York
If nothing else, the Americans can be persistent.