Actually the usual margin given by Canadian brokers to their Canadian clients is 70% (as opposed to the PDT 75%); there is no $25K rule and overnite maintenance is released immediately when positions are closed for use during the same day.
However, Canadian brokers cannot broker (legally) to US residents in the US without having US licensing and if they get US licensing, the SEC rules re PDT would apply to the accounts of their US resident customers.
As well,the account opening procedure in Canada would require you to provide Canadian credentials, including Canadian bank reference and domestic address, etc.
You could, however, be "temporarily resident" in Canada ..... its borderline, but people do it.