In his letter to his daughter, margaret, on 3/3/48 harry truman admits that in the four months that he was vice-president, he only saw president franklin d. roosevelt twice and they never discussed the american war effort. why are u.s. vice-presidents usually not involved in the highest levels of decision making?

Because they are not part of the president's cabinet. They are normally chosen to balance the ticket-attract votes from an area where the presidential candidate is weak.

Scholars have suggested a number of potential reasons for the downfall of Maya civilization in the southern lowlands, including overpopulation, environmental degradation, warfare, shifting trade routes and extended drought. It's likely that a complex combination of factors was behind the collapse.