Didn't the British ban colonization of the land west of the Appalachia and were the great lakes and Canada French speaking Catholics because IIRC Ontario only became anglicize because of the the British loyalist leaving the newly-independent US
There would be less impetus for settlement of Ontario by British colonists, as they could instead settle Ohio country.
Almost certainly. Its the Catholic migration that might be slowed down.
Irish Catholic migration would eventually pick up in the early 19th Century, however Continental Catholics migration is likely to slowed, Although I don't know what Britain's policy was on French migration to Quebec.
@Socrates
I am not so sure about Westminster representation, as it was very infeasible in the late 18th to mid 19th century. With the implementation of the Transatlantic telegraph, it would be very feasible, as that allows a fast line of communication, and the cost and speed of ships have improved.
I have thought about what the effect colonial decentralization would have on Britain, and it's hard to determine, as Britain wouldn't want to lose any population advantage it has over the colonies, however the social pressures of decentralization would be immense.
I tend to think the organization of this empire would be status quo, as imperial federation could be seen as infringing on autonomy, and giving up foreign/military policy to the imperial constituents could be seen as dissolving the empire. So a situation where Britain or England manages it's own internal affairs and the imperial/external affairs.