22 re Soviet BLoc weapons in Nam. It was their long range artillery, better than our 155s or the few 175mm arty we used there, that made the difference in the 1975 final offensive. Also we didn’t give the VNAF enough replacement aircraft, esp. F5s and Spookies, to make a major impact.
We abandoned the RVN when the Democrat-controlled US Congress cut off the funding. The Democrats told Nixon in 1969 that they would cease to fund the war. which left Nixon with very few options.
The US military was never defeated in Vietnam; rather, the Democrats in Congress surrendered to the NVA, which put the writing on the wall. I was in the USAF 1970-1974, and I have hated Democrats ever since.