The most devastating impact colonialism had on 19th and early 20th century China was on the Qing state. During the colonial era, the Qing state became politically, administratively and financially too weak to function as an effective government to lead the country towards a positive direction.
Imperialism had a profound and lasting impact on China. This made desperate British merchants sell opium into China in an attempt to rebalance the trade. The products that were manufactured by the Japanese in China were sold globally, hence made China richer which made China expand economically.