During the 1930s, the combination of the Great Depression and the memory of tragic losses in World War I contributed to pushing American public opinion and policy toward isolationism. Isolationists advocated non-involvement in European and Asian conflicts and non-entanglement in international politics.
More food= more people, more people means you need more food, which means you get people to make more food, which attracts more people, etc, etc.
I think the answer is colonization. Many European countries like Great Britain, France, Spain, and Portugal had started exploring the New World. These European Nations wanted to expand their territory and to spread religion and civilized barbarians in their colony.
