I look to NAFTA as evidence how this new agreement will be a setback in sectors of our economic expansion. DuPont had a polyesters plant near my hometown and as soon as NAFTA was passed, they began "downsizing" and offering early retirements. Many employees stayed on because they simply didn't have the years to qualify. DuPont "sold" the operation to a Mexican outfit (because as allowable under NAFTA, Mexico requires their nationals maintain controlling shares of businesses) and moved all the process equipment to Mexico.
In US beef sales, think of it this way - there are a limited number of metric tons of beef to be sold on the "world market" in excess of what US consumers purchase. When those other markets "open" and can only afford a break even price for the product, that open market will have the US and foreign consumers competing for US beef and who will end up paying more? US consumers because distributors will realize they can make up more than the difference from Americans and they'll view that difference as increased profits. Unless there is an adequate producer increase to keep up with both domestic and foreign demand which would help keep prices low, watch and see what happens. $8-12 lb for "high quality" beef will be commonplace.
If NAFTA was bad, why has the economy expanded at a rate of 4% per year since we signed it?