What is the 0.6% + 2%? Is that the currency conversion fee?
Any way you can get the US sales to be processed in USD and transferred to some kind of US bank account (Transferwise for example). That way you can re-use that to pay invoices in USD, or transfer it back in CAD at a better rate than what the processor is charging you.
I sometimes get paid in USD through paypal and that's how I reduce the amount I have to pay paypal for conversion fee.