From the perspective of the state as the unit of analysis, each country has its own external balance of payments. A country can earn revenue from others by producing internationally competitive goods and exporting them in large quantities; after obtaining such revenue, it can invest funds overseas and lend to countries that need capital for cross-border economic transactions. In this process, some countries become debtor states because of trade deficits, such as the United States, while others become creditor states by accumulating large trade surpluses, such as China. If the gap between deficits and surpluses widens, international payments will become imbalanced. Some countries can rapidly accumulate wealth while others experience outflows, creating difficulties in national financial structures and affecting the foundations of international power. To correct these imbalances, states will seek to reverse the situation through negotiations or policy measures, but disputes and misunderstandings often arise in the process, and further deterioration may affect the international security environment.