Tariffs: the bottom line, #1 contributing factor, is low cost of labor due to lack of labor laws overseas. The U.S. and other nations have all kinds of laws and regulations to protect the laborer, from OSCA to minority protection against discrimination. All that adds to the cost of having employees. Quite simply, China and others don't have 90% of those laws and regulations. Until that disparity is corrected, there will never be a level playing field and U.S. manufacturing will be at an insurmountable disadvantage.
Tariffs can be one answer. Presently, the U.S. doesn't want to tariff China because of foreign relations etc. There may be one possible excuse which could get by: linking a tariff to the disparity of labor protection laws. If China protests,world opinion will crucify them.