With regard to labour mobility, the U.S. business community is generally very supportive of measures to allow easier travel of professionals.
However, the political complications in the United States Congress are substantial in this area. I remember that the last time a U.S. trade agreement was negotiated was in 2003, with Chile and Singapore, and it included some visa provisions. It's not the ways and means committee but the judiciary committees that have jurisdiction over those issues. The U.S. trade representative at the time was raked over the coals and compelled to promise not to address those matters in trade agreements since then. I think that continues to be the case.
The case remains that Canada and Mexico, through NAFTA, have access to unlimited free professional visas—