NAFTA passed as an Act rather than a Treaty

The House of Representatives approved NAFTA on November 17,
1993, by a vote of 234 to 200. The agreement's supporters
included 132 Republicans and 102 Democrats. NAFTA passed the
Senate 61-38. Clinton signed it into law on December 8, 1993;
it went into effect on January 1, 1994.

Note that 61 is not 2/3 of the Senators present which is the
constitutional requirement to ratify a treaty. The "treaty"
was sent to the House of Representatives where it passed 234
to 200. I am not sure how an Act of Congress may affect Mexico
and Canada. The process itself smells!