This is a very interesting and significant observation by Trump. If this is followed up it could have a very big impact on interest rates in Canada because they're being held artificially low to provide a trade advantage.
It seems that Trump is starting to play hardball now that Carney's intransidence has attracted his attention. Up to present the Americans really haven't paid all that much attention to Canada and have been pretty tolerant.
Unfortunately the current liberal government under both Trudeau and Carney have made them start thinking more about Canada and our relationship.
https://americanfaith.com/trump-blasts-canadas-unacceptable-currency-advantage/