Final answer:
The Open Door Policy allowed the United States to conduct business freely in all areas of China, positively affecting U.S. trade with China by giving American companies an advantage in the Chinese market.
Step-by-step explanation:
The Open Door Policy had a positive effect on U.S. trade with China. It allowed the United States to conduct business within all areas of China. This meant that American businesses could trade freely in Chinese markets, without any special tariffs or transportation controls that would give unfair advantages to one country over another.
This policy greatly favored the United States, as American companies were producing higher-quality goods than other countries and were doing so more efficiently and less expensively. With the Open Door Policy, American businesses flooded the Chinese market with their goods, virtually squeezing other countries out of the market.