What was the reason for US bombing and incursions of Central and South America?

The US bombed central and south America, launched incursion into these lands, raping and killing thousands. They supported brutal dictators and ruthless militias, why was this done? please give both the American reason and the real reason?

The US has had millions invested in Latin America since the end of the nineteenth century. There were over 30 US military invasions and/or occupations in Latin American countries between 1898 and 1934, when FDR initiated a new policy. After WWII, the US created the School of the Americas in Panama, where most dictators were trained. They even had a Manual for Torture.
For over 150 years, the US policy towards Latin America has been violent, greedy and racist.