I did something like this in 1990, except we took 5 1/2 weeks and 19,000 km, and spent very little time on motorways.
Outbound - TransCanada to Winnipeg, north between the lakes, across Saskatchewan on smaller roads. Badlands in Alberta. Calgary. Icefields Parkway. Prince George. South through Okanagan then west to Vancouver. Ferry to the island, across to Tofino. Back south to Victoria. Ferry to Washington then all the way down the coast to LA, including Avenue of the Giants (redwood trees), several of the canyon roads northwest of LA.
Back - Angeles Crest Highway, Death Valley, Hoover Dam, Vegas (actually we just went around the city, couldn't be bothered with the tourist trap and didn't have $ for gambling), Grand Canyon, Utah, Colorado (Estes Park). After that we dropped down and took interstates 70 and 80 the rest of the way.
Outbound - TransCanada to Winnipeg, north between the lakes, across Saskatchewan on smaller roads. Badlands in Alberta. Calgary. Icefields Parkway. Prince George. South through Okanagan then west to Vancouver. Ferry to the island, across to Tofino. Back south to Victoria. Ferry to Washington then all the way down the coast to LA, including Avenue of the Giants (redwood trees), several of the canyon roads northwest of LA.
Back - Angeles Crest Highway, Death Valley, Hoover Dam, Vegas (actually we just went around the city, couldn't be bothered with the tourist trap and didn't have $ for gambling), Grand Canyon, Utah, Colorado (Estes Park). After that we dropped down and took interstates 70 and 80 the rest of the way.