China:
Believed that their land is heaven and there everywhere else was just darkness. That is why they stayed inside of their country for thousands of years, never venturing outside.
When foreigners came, the Chinese thought that they were inferior. When the European powers began to press and put more pressure upon the Chinese to trade with them, the Chinese attempted to kick them out.
Unfortunately, the Europeans discovered opium at this point and hooked half of China on it. The Europeans had a strangle hold on this product and used it like a prybar to force open China's gates.
Then a group of Chinese people who were angry at the Europeans got together and their combined effort to kick out the Europeans would later be known as the boxer rebellion.
This effort did not work out so well for the Chinese, while they did manage to scare some missionaries and burn some property, ultimately guns and cold steel won the day and the Europeans were now here to stay.
Japan:
The story of Japan is somewhat similar as well. They were very isolationist and did not like foreigners coming into their lands.
Japan opened up to foreign trade because of what foreign technology could offer. Before America came into Japan, Japan had a mostly feudal system of government dominated by noble warriors known as samurai.
These samurai really loved their swords and would never fight with dishonorable weapons such as poison and shurikens as ninjas did.
The merchants, however, having a greedy nature as most merchants do, wanted to sieze power for themselves. They saw the power in guns and decided to ask the Americans for help in establishing a more "modern" system of government.
Basically the Americans came, and wiped out the Samurai (see the Last Samurai starring Tom Cruise for a brief synopsis) and Japan became open to the western world for trade.
