There is a difference between the US Air Force Squadrons and US Army Squadrons. From approximately WWI thru the Vietnam War; US Air Force/US Navy Air Squadrons might have approximately 15 to 17...
20,351 Spitfires were built
there are either 6 or 7
Britain made 20,351 spitfires.
Depends on the country. Depends on what is airworthy. But, 12 to 14 seems to be the operational average