Some people, specially Chinese still believe that we defeated US just by guerilla tactics (hiding inside the tunnels and suddenly came out and killed US soldiers ), they just don't want to understand that US only withdraw from VN after her mighty air force was defeated over Ha Noi's sky in 1972 with many B52 bombers, equipped with the best jammers , well protect by Wild Weasel forces, were shoot down by obsolete SAM 2 (many SAM 2 were capture by Israel army from Egypt after 6 days war ).
Vietnam government claimed that she shot down 19 B-52 in the whole war. Obviously you have kind of misunderstanding of "many".
Furthermore, according to Wiki:
The USAF sustained approximately 0.4 losses per 1,000 sorties during the conflict, which compared favorably with a 2.0 rate in Korea and a 9.7 figure during World War II.