Complex sentence: Both were American foreign policies restricting Latin America from having any kind of relationship with the European powers at that time, therefore making the United States the sole supporter of the western hemisphere and the only country that could intervene in any "wrongdoing" to Latin America.
Split into simpler sentences: Both were American foreign policies restricting Latin America from reaching out to the European powers at that time and developing their own independent relationships with countries other than the United States. This made the United States the sole supporter of the western hemisphere and the only country that could intervene in any "wrongdoing" to Latin America.