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Now there have been several threads about how much of Mexico could the United States realistically annex after the Mexican-American War (the only reason they did not annex more than they did in OTL was because of the agenda of the diplomat who agreed the deal more than anything else).

Of the various threads I have read the most America could have taken without suffering too much of a military burden (In addition to their OTL Annexations from Mexico) is either:

1: Everything North of the Tropic of Cancer

2: The Rio Grande Republic, Coahuila, Chihuahua, Sonora, Baja California, Sinaloa, Nayarit, Durango, Zacatecas and San Luis Potosi

3: Everything North of 22nd North Parallel

However I have as of yet I have not found a thread on how much America can take off Mexico if Quebec and Nova Scotia joined the ARW, were part of the founding members of the USA and remained as part of it to this day ITTL.

The likely butterflies of this are that intolerance of Catholics is likely to be a lot less (although the race issue is likely to remain, how much depends on the butterflies), the free states are bigger in numbers than the slave states from day 1 and the Federalists remain a political force which in turn means that more effort is put into developing the US Economy, Infrastructure and Military.

Now considering that the anti-slavery side is bigger and there is more migration outward from the East Coast in pretty much all directions than OTL it is highly unlikely that there would be uninterested in Mexico due to the potential land and the potential slaveholding states to prevent their disadvantage against the Free States becoming ever bigger.

So they will be very interested in expanding into Mexico, the question I want to ask is how much considering these ITTL circumstances?

My view is that at least option 1 can be done with 2 and 3 likely in this case at least, but would these circumstances allow for the Cession itself to go beyond option 2/3? If so by how much?
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