the US armed forces lost 60,000 men on the battlefields. 150,000 US soldiers committed suicide after returning home, plus 300,000 men were wounded, with 100,000 ended up as invalid. the US army never lost a battle? let see.
Lost Battles of the Vietnam War
sure, USSR and China backed North Vietnam. But do you know who backed and supported the superpower America? they came the western world, including fighting troops from South Korea, Philippines, Thailand, Australia and New Zealand. not to mention South Vietnam.
the weapons North Vietnam received from USSR and China were just a big water drop in the ocean. the military imbalance during the war was probably 1:20. in favor of the US.