What policy expanded American trading interests in China?

Imperialism explains the overseas economic interference of the US in Asian affairs. In its time, however, the US was keeping in step with other major political and economic powers such as France and England. The US, however, could have more wisely developed its own resources it had in its homeland. At the time, and decades before and after imperialism, the US was protected from world powers by two vast oceans. The US had a large and growing population and inventors and business men to make a huge impact on non imperialism adventures.