Canada had an open invitation to join the the United States when the Articles of Confederation were written, before the Constitution even existed.
Article XI of the Articles of Confederation:
“Canada acceding to this confederation, and adjoining in the measures of the United States, shall be admitted into, and entitled to all the advantages of this Union; but no other colony shall be admitted into the same, unless such admission be agreed to by nine States”
That provision allowed residents of Canada to petition the United States for inclusion in the Union, if the Canadians ended their relationship with the crown.
This invitation essentially ended with the writing of the Constitution.
People panicking about Trump jokingly floating Canada’s addition to the Union are falsely attributing this to the Club of Rome, or the NWO North American Union, to usher in the AMERO, (which was supposed to included Mexico), don’t realize the open invitation of Canada to the United States predates even the Constitution itself.
Mike