The north/south route along western North America is typically mountainous, or at the least quite rugged. The region is beautiful when the weather is nice, and horrific if you're stuck flying in deteriorating conditions. Obviously, we are all trained to plan and avoid poor weather beyond our, and the plane's capabilities, but in that region, the spaces can be much greater between suitable landing areas. If you have to divert, your alternate choice may have gone down too. When you actually plot the distances between airports, it can be a little alarming north on the 49th parallel. When I ferried an MD500 helicopter from central Alaska to Vancouver, there were not adequate fuel stops for the range of the machines, and we had to plan off airport stops to jerry can fuel along the way. Fairly easy in a helicopter, not so much so in a wheelplane. If your planning is good, and the weather holds, it's doable in any rentable GA aircraft.
It could be that flying within (as opposed to over) the mountain valleys seems attractive. You
really have to know what you're doing, and where you're going to do this safely. The valleys can box you in, and dead end if you choose the wrong one, leaving you inadequate room to turn around to exit. I've had friends die getting this wrong. I am only comfortable flying the Canadian Rocky Mountains if I can go over, rather than through the valleys. I have flown the valleys too, but with good local knowledge, and a plan to get out the other way.
Thereafter, you must consider a forced landing, there are few places to do it without damaging a typical tricycle Cessna/Piper, help may be 50+ miles away, and it can be difficult to make yourself findable. For these routes it's important to carry enough emergency kit to survive for several days. If you're renting the plane, you'll have to buy everything. Even when I flew a same day ferry flight of a 182 from Oregon to Vancouver, I bought the necessities at a local camping store in Oregon. This included a life jacket, in case ditching was my only choice.
The western areas are adequately served with fuel all the way, which is good. In northern Quebec in the east, fuel becomes the problem, there are just not enough places to stop to refuel, and only a couple of runways at the far north.
I can't answer specific questions about insurance, you'll have to ask the aircraft provider. But assure that the insurance will cover the intended route, and beyond that, have a plan for what happens if you land the aircraft into a place from which a ferry out is not possible. That could be as simple as you landed somewhere with no fuel availability, and fuel had to be brought to you, to damage to the aircraft which requires maintenance beyond the resource of that place. I have the fortune (and duty) to be among a group of experienced pilots who would move heaven and earth to help another. If you're in a foreign place without "help", it can be more difficult.
A few photos I have posted here:
http://www.pprune.org/private-flying...te-flying.html
will give you a sense of the remoteness and lack of facilities in the north....