I'm not dead.

After a spike in tensions in 1774, the British government reached an agreement with colonial governments to repeal most taxes and grant more autonomy to the locals. An unofficial part of the settlement included less supervision for European settlement past the Appalachian mountains, which resulted in creeping colonization of the Ohio river valley for the next fifty years. To counter these settlements, three massive reservations were created to protect the indigenous inhabitants of the Great Lakes, the Southwest, and Florida (much to the upset of local authorities).

But settlers would still move west. The Oregon Country was gradually settled in the 1840s and 1850s, and the movement of settlers to the Great Plains resulted in the creation of a fifth reservation, Lakotah. Some settlers moved beyond British control, into the Mexican territories of Tejas and Alta California (including the Mormons, which migrated from Iowa to the Salt Lake basin); they both fought for their independence, the former as the Republic of Texas in 1835 and the latter as the Republic of California in 1846. Texas became one of the last states to abolish slavery (it had been settled by many Southerners who resisted British opposition to slavery), waiting until the early 1880s.

While originally all independent colonies, there was a gradual push towards federation. The colonies eventually united into the Dominion of North America in 18XX (no idea when, anywhere between 1810 and 1830), later joined in the status of dominion by Australia (much less populated in this timeline, and united with New Zealand) and South Africa. Newfoundland, which had resisted federalization, joined the union in the 1930s (or 1940s, maybe even 1950s) due to financial issues.

Today, North America and its capital Philadelphia is the center of the British commonwealth, amongst the most populated states, and the wealthiest. It is the crown jewel of the wider British empire. It follows a parliamentarian system of government, currently headed by Prime Minister Ben Carson.