Looking through the Canadian Prius v manual it doesn't appear you can change... http://s3.amazonaws.com/toyota.site.p01/toyota/manuals/OM47B23U/OM47B23U.pdf
There is a button on the dashboard of our early (2012) U.S. market Prius v to switch between mph and km/h but the button was discontinued after a few model years. You're not the first to complain about it. Perhaps it can be switched through Techstream but you wouldn't want to do that every time you travel back and forth. I found it pretty easy to learn to mentally convert between mph and km/h when I owned a European market Mercedes in the U.S. many years ago. Even during the many times we've driven U.S. market vehicles in Canada, I've not bothered to look at the little km/h speedometer inside the mph speedometer - I still unconsciously mentally convert between km/h and mph. Edit: I looked at the online sales brochures for the U.S. market Prius v and saw that 2017 was the first model year in which the km/h to mph switch button was discontinued. The button was formerly to the left of the emergency flasher button and was replaced with a "blank". If your Canadian market 2017 Prius has the same "blank", it might be possible to install the button switch used on a previous model year Prius v if the switching feature is still available in the vehicle electronics - but that is a long shot.
The first wave of 2016 Prius (regular hatchback Prius) were missing a mph/kmh function, there was a clamor, and it was rectified. With the Prius v the ability was discontinued, and that's just the way it is? Too, I'm not sure which is worse: not having the function at all, or having it, but buried several levels deep in a touch-screen.
Yeah I wasn't going to trot something out, but: Too, I don't suppose the above style ever failed, leaving you to buy one from a guy on EBay, with "approximately" the same number of miles on the odo.
We have MPH/Km-h switch on our 2016 Prius v Three. It came in quite handy earlier this year when we were in Canada...
The part number for the switch assembly that appears to contain both the km/h-mph switch and hazard switch appears to be 84330-47070. According to the parts list, it was used on the Canadian market Prius v manufactured 11/2014 - 04/2016. I would be surprised if the 2017 Canadian market Prius v still has the wiring and other electronic circuitry that enables the km/h-mph button to function but I suppose it is possible. The switch module is fairly inexpensive. According the a parts number cross reference, the same switch assembly is used on both U.S. and Canadian market vehicles. I see it priced under US$60 on some part seller websites.
Not that it helps the OP, but I just noticed in the Canadian market Prius v owners manual for the final 2018 model year that the km/h to MPH button returned. It's not shown in the 2017 owners manual for Canada. It's odd that it would be deleted for only one model year but maybe it was restored due to complaints.
