You asked, Where does it say we have to support the rest of the hemisphere?
Section 3 of Cronyn's bill, I believe.
Senate Bill 2941. Sen. Cronyn Establishing a N. American Fund
http://thomas.loc.gov/cgi-bin/query/z?c108:S.2941:
Highlights:
SEC. 3. PURPOSES.
The purposes of the Fund shall be--
(1) to promote economic and infrastructure integration among Canada, Mexico, and the United States;
(2) to promote education and economic development in Mexico; and
(3) to reduce the wealth gap between Mexico and Canada, and between Mexico and the United States.
More:
SEC. 4. PROJECTS FUNDED.
(a) IN GENERAL- The Fund shall make grants for projects to carry out the purposes described in section 3, including projects--
(1) to construct roads in Mexico to facilitate trade between Mexico and Canada, and Mexico and the United States;
(2) to develop and implement post-secondary education programs in Mexico;
(3) to install telecommunications technologies throughout Mexico; and
(4) to construct other infrastructure that will carry out such purposes.
More:
SEC. 5. CONTRIBUTIONS TO THE FUND.
(a) IN GENERAL- The terms of the agreement establishing the Fund shall, subject to the limitation in subsection (b), require the Governments of Canada, Mexico, and the United States to contribute to the Fund.
Hell, they can't even manage to get their citizens through elementary school and they've got plans to spend our money for "post-secondary education programs"? What a joke.