It would be a disaster for US, because US enjoys benefits of printing as much money as it needs to purchase anything from abroad exchanging zeros and ones that cost nothing for real natural resources and goods from other countries.

Just about any country leader that announced plans to stop using USD for trade, was killed in some way.

Or, if USA isn't brave enough to openly attack the country, they declare it "hostile" and try to suffocate using sanctions (e.g. Iran).