"the american continents . . are henceforth not to be considered as subjects for future colonization by any european powers." what did this 1823 statement by president james monroe indicate about the united states' role in the world? a. the united states had become the leading diplomatic negotiator. b. the united states ended its friendly relations with european countries. c. the united states had become the dominant world power. d. the united states began to exert dominance in the western hemisphere.