What were the major goals of US foreign policy makers in the first two decades of the twentieth century?
The United States at that time was a brand new empire, having very recently taken the colonies of Spain, so you could say that one major foreign policy goal at that time was for the new empire to assert itself on the world stage in competition with the other empires. This would explain the Open Door Note and the Roosevelt Corollary, which one might describe as aggressive policies towards the British and French empires, among others, in Asia and the Caribbean.
America also staked a power claim in the world to solidify imperial gains by projecting military power outside the US. The Great White Fleet sent this message, while US Marines in Central America and the Caribbean were used in a more practical sense to protect American economic interests in that region.