Scratch, this is what you get on answers.com:
Manifest destiny was obviously a defense of what is now called
Imperialism. It was a complex set of beliefs that incorporated a variety of ideas about race, religion, culture, and economic necessity. Some people, like the land speculators that settled in Florida, Texas, and Native American lands, wanted more land to get rich. Some fled poverty in Europe and eastern metropolitan centers.
Some assumed that without spreading out to fresh lands the nation would languish. Some sought to perpetuate the institution of slavery by expanding it to new territories. Some believed that expansion into "uncivilized" regions would spread progress and democracy. It was convenient for all to think that they had the divine right to acquire and dominate because they had the proper economic system and the most developed culture and belonged to the most advanced race.
What were these ‘new, uncivilized territories’? According to Wikipedia, these involved many other nations.
Sometimes Manifest Destiny was interpreted so widely as to include the eventual absorption of all North America: Canada, Mexico, Cuba and Central America. It has also been used to advocate and justify other territorial acquisitions. Advocates of Manifest Destiny believed that expansion was not only good, but that it was obvious ("manifest") and certain ("destiny").
We are very much talking of world domination (or at least domination of other nations in North and South America) when it comes to the concept of Manifest destiny.