I would say it's harsh. The great lakes made up 16% of the US GDP in 1815, and losing 4 of the 5 will mean a contraction of 13% of their economy at least. Losing a fifth of their total lands, and giving up so much investment. Their economy is bust for the next decade or two.Well so you chose the mix of medium to soft. With little adjustment for BNA.
It will make Canada that much stronger and richer since it now has access to all the lakes. A canal connecting Lake Ontario to Lake Huron needs to be first order of business.
Question will Americans still be welcoming to emigrants? What about emigrants from British isles?
With an antagonist US will the British protect Spain from American attacks. First would be florida. That be the first goal of the Americans.
now will the attacks by the Americans on the southern tribes trigger a war with the native confederation to the north? Waiting to see.
will the British open more of BNA for settlement? Will they encourage industry to be created or we going to see British investment in New England at the expense of BNA.
what we do know is that Britain has both a friend and bitter enemy in North America.
The others, well those would be spoilers!