When creating multi-currency transactions - either invoices or payments - the Rate Type is what determines the exchange rate and operation for the other currency. The batch amount is entered as the currency of the vendor, and the exchange rate determines the home currency (CAD) equivalent. Since you want to multiply the US Dollar amount for your US vendor to get the CAD equivalent, you will have an Rate Table with the Operation of Multiply, and the rate in the Exchange Rates table will be around 1.16 or so.

So if you are creating a payment and want to multiply the exchange rate to the US Dollar Payment amount, you need to make sure that the exchange rate from the Finder is selected with an associated Rate Type based on the Multiply rate operation. By default, the Rate Type comes from what was set on the Bank but it can be changed from the exchange rate Finder.

Printed Checks do not show Home equivalent amount, so you must mean posting checks that shows the reverse. There are no problems with posting checks (manual or system checks) and getting the operation reversed, so make sure that the rate type on the payment is what you expect - the same as for the invoice.