Ethnocentrism is when you believe that you are superior to others. This is often because they are isolated. But there are many perks to this. There's a lot of natural resources, there is often a surplus of natural resources. They are strong and everyone has similar cultures. Their goal is to keep foreigners out.
The Opium War is when Europe wanted control of China because of their natural resources. So, Britain gets the people in China addicted to opium so they could trade with them. The results were that Britain wins and now has bigger weapons. They can trade with China now.