China is by no means the only entity that might or could use EMP. Nkorea could as we speak and they have a ruler that has no compunctions about killing people. Iran will have the capability shortly if they don’t already. They have a fatalistic ideology and are looking foreward to the end of the earth. Taliban, AlQaeda other terrorist groups, any of them could pull it off.
If we have a financial collapse and our money is worthless China will still want to be paid like a loan shark. When we can’t they will try to cut are balls off.