Answer:
Manifest Destiny
Overseas expansion forced America to confront conflicting sides of its collective personality — one championing self-determination, the right of people to rule themselves — rooted in its own emancipation from British rule in the late 18th century; the other based on its own sense of mission to spread its way of life and need for economic growth.
Nineteenth-century expansion played out under the ideological cloak of Manifest Destiny, the belief that God destined white Protestants to dominate inferior Indians, Mexicans, and Asians. Senator and historian Albert Beveridge said, “God has marked the American people as His chosen nation to finally lead in the regeneration of the world. This is the divine mission of America, and it holds for us all the profit, all the glory, all the happiness possible to man.” His message echoed a sense of mission and prerogative that traced back to 17th-century Puritans, and one that resonates with many Americans today. While religious nationalism might sound chauvinistic to some by today’s standards, keep in mind that most powerful empires believe God likes them better than others
Hawaii
With their expert knowledge of currents, stars, and wind, Polynesians from Marquesas and Raiatea migrated to the Hawaiian Islands in double-hulled voyaging canoes sometime around 500 CE. They brought with them the fishing and farming techniques, language, religion, social hierarchy, tools, and outrigger canoes common to what’s now French Polynesia. Another wave from Bora Bora and Tahiti settled in the 11th century. Following the same currents, British explorer and naval captain James Cook visited Oahu and Kauai in 1778 on his Third Voyage.
Japan & Korea
Further west, the U.S. had no pretensions of taking over Japan the way it had Hawaii. As mentioned above, the U.S. fleet of four warships under Matthew Perry sailed into Edo Harbor (Tokyo) in 1853 more in search of trade than territory. They also hoped to build coaling stations for the steamships Japanese called the “giant, dragons puffing smoke.” There wasn’t a lot of dialog at first other than the unspoken gunboat message. Perry just presented a letter (in English) from President Millard Fillmore demanding that Japan open its ports for trade and returned in 1854 with more ships. Japanese were divided amongst themselves during the Bakumatsu era of transition and factionalism between traditional shogunate rulers and ishin shishi that wanted to expand through more Western-style imperialism. The island had been mostly closed off to the outside world for centuries, other than a small island port at Dejima opened to Dutch trade.