I found that not all VPNs work equally well for Netflix. The one that I've used in the past and worked great for Netflix on my iPhone and iPad is VPN One Click (Professional).
Basically you toggle the VPN ON or OFF. When ON, when you get into the Netflix app it's all US content. With VPN OFF, goes back to Canadian content. It was nice because it was quick and easy and worked flawlessly, especially when I was shuttling frequently between US and Canada content.
It also has non-US servers to choose from if you like European or other sources of media.
If memory serves me, I think it gives you a 7 day trial when you install the app. You can try it before going monthly or yearly.