British Compromise

POD (1766)
As part of a compromise agreement negotiated and supported by Prime Minister William Pitt (the Elder), the British government admits members of each colony into Parliament as voting observers, thus giving "taxation with proper representation", and diffusing the crisis (the hated "Townshend Acts" never occur). The agreement stipulates that the colonies' Governors would still be appointed by the Crown, but would also be approved by the Parliament of each Colony. With a thusly united Empire, the British is set to go on to colonize the world, much as they did in our timeline, but with the support of all of North America behind her. 1770s- the American members of Parliament begin to have greater influence in the British Parliament, and are taken more seriously than at first- though most are still considered outsiders.

Americans get their own parliament (March 1767)
As per the terms the Americans imposed to agree to the higher tax imposed by the British after the French and Indian war, on March 12th, 1767 Britain's parliament enacts the "Continental Parliament Act", which establishes a Continental Parliament and "Articles of Government" for North America. The delegates to the parliament are to be selected by the Royal Governors of each Province and they are to meet in Philadelphia the following Spring, which is considered a good middle ground for the North American colonies. Now the American parliament is created, but foreign affairs like war still ultimately go to the British parliament for approval or denial.

Americans begin expanding west (late 1700's/early 1800's)
American parliament passes the "American West" act in 1791, allowing Americans to begin expanding west past the Appalachians. These areas of settlement become known as "territories", areas that were supposed to be governed by the "Owner Provinces", although the provinces can't actually keep very good power do to distance and land barriers; these territories often end up having overlapping provincial claims, so some say there were more than the 4 recognized territories (Southern territory, Ohio territory, Michigan territory and the Midwest territory).

Dominions form a Federation in North America (1815-1820)
The Americans started demanding more autonomy in the early 1800's, and the British felt the time was right for some form of independence in North America. Negotiations began in 1815, and over the course of five years a pretty good neutral decision was made. The British and the Americans agree to a new Federation in North America, loosely uniting the 3 Dominions and the American territories: the Thirteen Colonies, Lower Canada (Quebec), Upper Canada and the American western territories. The Dominions gain some say in their foreign affairs, and also gain full internal and external affairs control over the Federation they belong in, with the Federation only taking orders from the British in times of war. The parliament for the Federation is centered in Boston. The Current Government System
 * Monarch - If a bill makes royal ascent the Monarch will be the one to read over and approve or deny the bill. The Monarchy is losing power during this time, however, so this may not last.
 * British Parliament - The overseers of the entire empire's affairs, the British Parliament are a tireless bunch who work closely with the new Dominion system, as well as the colonies and homeland. War declarations and some external affairs for Britain's Dominions are handled by the British Parliament.
 * North American Parliament - Once a bill effecting all 3 of North America's Dominions is drawn up it must go through those Dominion's parliaments, where if it gets a majority 2/3 approval it then rises up to the Federational level. The North American Parliament will then either approve or deny the bill, and make it a law for all 3 of North America's Dominions.
 * Dominion Parliament - The parliament for each Dominion handles that Dominion's internal affairs, and bills that will only effect that specific Dominion. Most notable of these is the American parliament.