Originally Posted by
televisor
Not on UA, at least not when I tried to book a number of tickets at the end of 2015. I keep getting repriced to a more expensive ticket when the UA website realised my credit card wasn't US - but booking through expedia.com worked without issues. (Since then I have gotten a US credit card, so I have more flexibility.)
It's entirely possible things have changed since 2015 though.
Some fares are restricted for sale in certain countries, and as I noted inventory differs. So it's absolutely possible to get a reprice if you change sales city.
But in general the "Canada/Europe has cheaper J fares" phenomenon is based on the origin city. You have to be booking a RT ex-Canada or ex-Europe, regardless of where you buy the ticket. In fact, the entire fare table is just different much of the time.