This does not affect players on US servers living in the USA or Canada, for example, or any players on EU servers.
The announcement is pretty clear as is, especially with the above thrown in.
It also says:
"This affects all players on US servers living in the following countries
whose domestic currency is NOT the US dollar:"
It doesn't say
"This affects all players on US servers living in all countries whose domestic currency is not the US dollar"
It even gives you a handy list where Canada isn't listed.
However, I think there are some minor changes to Canadians buying diamonds for the US servers, but not nearly as large as the changes to people in the EU and UK buying diamonds on US servers.
Canadian difference is +/- maybe 10 diamonds on packages, hence not really important to include.
EU/UK difference is mostly less many hundreds of diamonds on packages.