In World War II, the United States had outstanding fighters like the P-51 Mustang and the P-47 Thunderbolt. Allies tossed in excellent aircraft as well, like the Spitfire.
But while the Allies won the air-to-air battle against the Axis, it doesn’t mean that the ground troops could forego ground-based air defense.
The U.S. had one weapon that they used for that role — especially front-line grunts. It was the M2 machine gun, known as “Ma Deuce.” One could do some serious damage, firing up to 635 rounds per minute according to the FN website.