We do have an unspoken deal with nations like Japan, Saudi Arabia, Korea. They buy our TBills and we defend them. IOW they help prop up the US Dollar
Trump’s angle on this is that we allowed ourselves to get manipulated by China. He didn’t say it but I suspect he will push for higher import taxes and reduced regulation domestically to get us back in the game. His message is you have to give to get and the Chinese are getting all the value of our market almost for nothing. He said we hold all the cards ( in other words they need our market) and we are letting them have it. He indicated that he is experienced working with creditors and understands that working relationship and will not allow this situation to continue.