The amero is a made-up word that people sometimes use to describe a hypothetical currency that would be used by the United States, Canada, and Mexico if they ever decided to join together in a big club like the European Union. The word "amero" is a mashup of the words "America" and "euro," since the euro is the currency used by most of the countries in the European Union.
Basically, some people think that it would be a good idea for the United States, Canada, and Mexico to band together and create a super-country like the European Union, with open borders and shared laws and a whole bunch of other things that would make it easier to trade and travel and stuff like that. And if they did that, they might decide to create a new currency that they could all use, instead of sticking with the U.S. dollar, the Canadian dollar, and the Mexican peso.
Now, that's all just speculation and nobody knows for sure if it will ever happen. But if it did, it would be a pretty big deal! People would have to figure out how to convert their old money into the new amero and everything would be priced differently. It would be like when your mom and dad take you to a foreign country and you have to figure out how much money you have in the local currency. But on a much, much bigger scale.