Great locations! The timing is a little off, though. I'll just add some information for you to think about. If you do go ahead with your plan, make sure to bring wet & cold weather clothes and plenty of time for a flexible route. If you have flexible dates, I would say you would have a better trip if you went a slightly different time.
I would push the whole thing out to start in mid- or late-April, or reverse it and start in July in Canada. The latter is pretty much what I did on my first tour, and I had great weather. I started July 4 in Colorado, road up to Jasper, then across British Colombia, then down the Oregon & WAshington coast to end in NOrthern California.
March/April is too early for the Sierra (California mountains, Yosemite, Tahoe), the ridable passes from the east side over Yosemite to the west side don't open until end of May. (Look up Tioga Road opening dates.) It's still the end of ski season in March, you might have OK weather, but you could still have snow on the mountain passes.
Southern California, Arizona and New Mexico are good that time of year. Death Valley is not a bad idea - I haven't done it so I don't have much to add, but people do ride there. Be aware of long distances between water sources and plan accordingly. GO to Joshua Tree National Park near Los Angeles too, if you head that way. Watch out if you think about going to the Grand Canyon or the Adventure Cycling Western Express Route through St. George, those are high elevation places and will get snow and cold weather still in March/April.
Montana and Wyoming are still spring conditions as late as the start of June, and I would have to guess that it's a little on the early side for Banff/Jasper as well. Take a look at the opening dates for Going to the Sun ROad (GLacier) - the last 2 years were late June.
Oregon/Washington/BC is still going to be rainy in March/April. The Pacific Coast (CA/OR/WA) typically has a northwest wind, so heading north on the coast means headwind. Most people ride south.
I really don't mean to be a bummer here, but if you can shift your dates around that would be better. Or change your plans to start in Southern California and ride in AZ/NM/Utah until a little later in the season, then maybe get onto the Adventure Cycling Great Parks route in June/July. Your original locations are nicer country (especially given your username!), but you may as well be realistic about the weather.