The Amero is not (as of yet anyhow) a valid currency to pay your US tax obligations with. IT is at this point a “currency” that is believed by many to one day replace the greenback – US Dollar – when the value of the US Dollar declines to insignificance. It is not (again as of yet anyhow) recognized as a valid currency in the broader market place.
With the rate at which the USA is printing money to bail it self out of 8 years of financial mismanagement and lack of proper fiscal oversight from the administrative branch of the national government over greedy wall street schmucks.
There seems little doubt based on the economic precepts of supply and demand that over the next decade or so the value of the US dollar in relation to other currencies may very well go down substantially. Unless of course other countries race their currency to the bottom faster than the US can devalue the greenback.
Proponents of the Amero have a valid concern in their lack of faith that the US dollar will maintain its value.