manifest destiny

Short definition from Wiktionary

Noun

1. 1
   The political doctrine or belief held by the United States of America, particularly during its expansion, that the nation was destined to expand toward the west.
2. 2
   The political doctrine or belief held by many citizens of the United States of America that their system is best, and the idea that all humans would like to become Americans.
3. 3
   The belief that God supports the expansion of the United States of America throughout the entire North American continent except Mexico.
4. 4
   Alternative letter-case form of manifest destiny.

Verb

1. 1
   To exercise and realize manifest destiny; to enable the cultural and political expansion of the United States of America.