Its US that force their allies to choose other currency, not China forcing them.

When US print money(aka paper), US want goods, you keep paper, US keep goods, then US print more money, USD on your hand devalue, technically you are giving free goods to US. When half of the world stop accepting USD, that means US will take 2x from you, assuming US consumption is the same. then 2/3 world stop accepting it, and you still accepting USD, then US will take 3x from you. So basically when half of the world stop giving to US, the tread will quickly change.