Generally, the US has a goods deficit with its NAFTA partners; that is, it imports more goods from them than it exports. On the other hand, the US generally has a services surplus with its two neighbors, i.e. it exports more services to them than it imports. As in any trade agreement, there are winners and losers.
Unlike the EU and Eurozone agreements, NAFTA does not allow the free flow of people across borders. The three member countries also did not adopt a single currency. It is more of a simple trade agreement. A suitable political atmosphere did not exist to make the agreement a true political union.