It is difficult to quantify because different countries work under different rules(for example China doesn't have OUR EPA). Because the equation has so many variables, you can't pinpoint one thing for a single cause and effect. So to make a generalization either way is dishonest. Our economy was on the track for disaster because of deficit spending, a bloated government (with too many generous pensions), too many give-away programs, and reckless spending on government projects. So, while free trade has a small part in our economic woes, it is minimal.
Why does every “Free Trade” agreement include money to retrain “displaced” US workers?