Will the U.S. Dollar strengthen if?

Other sovereign countries use the U.S. Dollar as their official currency. I learned that the sovereign nations of Ecuador,El Salvador, East Timor, Marshall Islands, and Palau uses the U.S. Dollars. Also U.S. territories such as Guam, Northern Marianas, American Samoa, Puerto Rico and the U.S. Virgin Islands uses the the U.S. dollar, does this have a postive or negative effect in the American Economy?