A trade war with China will hurt the world economy. China will...

A trade war with China will hurt the world economy. China will produce and sell less, and buy less raw materials from countries like Australia. Moreover, other counties may also join the trade war.

China can hurt the US economy using a number of ways not just using tariffs. They can stop accepting US dollars, stop lending them money, interfere with their overseas interests and support the enemies of the USA (cold war). They can even start proxy wars in other countries. The stakes are high.

If countries stop accepting US dollars as payment it will hurt the USA big time. Their currency will depreciate and they will no longer be able to print money to pay their debt. Just like any other country, they will need to buy another currency to pay their debt. ​