Congress placed a $1 billion ceiling on military aid to South Vietnam for fiscal year 1974. This figure was trimmed further to $700 million by August 11. Military aid to South Vietnam in fiscal year 1973 was $2.8 billion; in 1975 it would be cut to $300 million. Once aid was cut, it took the North Vietnamese only 55 days to defeat the South Vietnamese forces when they launched their final offensive in 1975.
The biggest failure was not to defend South Vietnam as we promised to do if the North Vietnamese violated the Paris Peace Agreement. The ARVN suffered a total of 254,256 combat deaths.
Question is where did all those spare parts and ammunition go? They don't expire just because aid was cut back.
During the 75' invasion, ARVN was trying to reload spent brass and was even washing and re-using bandages. Ammunition expenditure was strictly rationed.
Not nearly enough gas either but this can be blamed on the mid 70s oil crisis.