Britain's Royal Navy controlled most of the key maritime trade routes and enjoyed unchallenged sea power. Alongside the formal control exerted over its own colonies, Britain's dominant position in world trade meant that it effectively controlled access to many regions, such as Asia, North America, Oceania, and Africa. The British also, much to the dismay of other colonial empires, helped the United States uphold the Monroe Doctrine which upheld its economic dominance in the Americas.