US to Canada circa 1777: you're in if you want

In reading the Articles of Confederation for my Constitutional Law class, I came across an interesting little tidbit in Article XI, which reads as follows:

Article XI. 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.

Basically the United States was explicitly saying that United States would accept Canada as a new state if Canada wanted to join the United States. This in and of itself is kind of cute but added to another thought experiment it becomes even more amusing. In my Constitutional Law class we have been discussing whether or not the Constitution was validly adopted based on the matter that the means in which it was adopted were in violation of the, then in effect, Articles of Confederation. If the Constitution were to have been illegally adopted then it would follow that the Articles of Confederation are still valid to this day. Between all these facts we have the situation that it could be argued, with some validity, that Canada has the right to join the United States to this day and that all Canada would need to do would be to say they wanted in.