The use of treaties for trade has been almost nonexistent after 1890 when the Congress gave the President authority to negotiate tariffs and suspend duty free tariffs. That decision was challenged and the Supreme Court of the United States (SCOTUS) upheld that Congress did not usurp their constitutional powers to the President. This decision would serve as the basis for legislation that would give and restrict the Presidents power over the years.
This later became known as the Congressional-Executive Act, which differentiated itself from a treaty which requires the 2/3 majority vote in the Senate. It is this Congressional-Executive Act that has been used for almost every American trade deal since the 1890s.
SCOTUS also sided with Obamacare and other unconstitutional actions.