Complex sentence: With the fall of both Cambodia and South Vietnam in the spring of 1975, the political climate between Washington and the government of PM Sanya had become very sour, and the USAF was wanted out of Thailand by the end of the year.
Split into simpler sentences: With the fall of both Cambodia and South Vietnam in the spring of 1975, the political climate between Washington and the government of PM Sanya had soured. The Thai government wanted the US out of Thailand by the end of the year.