Original sentence: A concern with any unified North American currency is the differing economic situations between each country.North America on the other hand has three distinct economies; one based mainly on agriculture and manufacturing, with a demand for free trade (Mexico), another based on services such as retail, with low taxes and low public spending (United States), and a third based on services with higher taxes and higher public spending, with a large sector in primary goods such as oil, mining and lumber (Canada).The Eurozone is broadly similar being service-based economies  based on high public spending (compared to the United States), high taxes and wealth being created by the sale of goods and services
Edited sentence: North America on the other hand has three distinct economies , one based mainly on agriculture and manufacturing, with a demand for free trade (Mexico), one based on services such as retail, with low taxes and low public spending (United States), and an another based on services with higher taxes and higher public spending, with a large sector in primary goods such as oil, mining and lumber (Canada).One possible problem with a North American currency union is the differing economic situations between each country, while the Eurozone is broadly similar being service-based economies  based on high public spending (compared to the United States), high taxes and wealth being created by the sale of goods and services