The Euro made good sense, as there were over 20 countries in the area, each with its own currency. The Amero makes less sense. While Germany, Italy and France are all similar in size, there is a huge economic difference between the US, Canada and Mexico. It would be a disadvantage most of the time for the Canadians and the Mexicans because of this disparity, and politically, it would be very divisive in the US among various regions and factions.