It would be sad (or should I say, even sadder) if the Mountie replaced Cavalry, which it is weaker than. The bonus for Natural Parks is not very useful, because you're not likely to ever be fighting near one. I think I've built maybe 2 National Parks ever (and not for lack of trying), and I don't think I've EVER seen the AI build one.
I usually get 1 or 2 in most culture games I play - more if I've got the Eiffel Tower, some tundra cities, and/or a good faith source. If I'm pretty densely settled in my cities though, they can be a challenge. For the AI especially I can see it being a challenge - even with a good location appeal-wise, you often have to rearrange ownership of tiles between cities and/or remove improvements to be able to build one, which I doubt the AI would do.
Oddly, tundra cities usually get a number of my parks - tundra plus mountains is usually a good appeal combo and I don't have much build on them (see Alaska I guess). Canada's ability to build farms on tundra is then going to make them less likely to build national parks in the areas I find the easiest.