Let's just compare to the Monroe Doctrine [1]. What this actually means has gone through several iterations by since I think Teddy Roosevelt's time, it's that the United States views the Americas (being North and South America) to be the sole domain of the United States.
This was a convenient excuse for any number of regime changes in Central and South America since 1945. The US almost started World War Three over Cuba in 1962 after the USSR retaliated to the US putting nuclear MRBMs in Turkey. We've starved Cuba for 60+ years for having the audacity to overthrow our puppet government and nationalize some mob casinos. Recently, we kidnapped the head of state of Venezuela because reasons.
But sure, let's focus on China militarizing its territorial waters.