Hey us Rednecks even have internal flushing toilets now ya know!
All joking aside ....... we always carry US$ cash when we are down in the USA in case one of our cards got compromised, as it has or the card system was down, which has occurred at a gas station a couple of times. I'd strongly consider always carrying a certain amount of the currency of the country I'm visiting just in case.
Some small towns with mom and pop type stores, or farmers markets you might visit may still be a cash only deal, but it is pretty rare in today's age. There are still a lot of Canadians that have never ventured south of the border to realize the worth of a US dollar or familiar with current rate exchanges.
We rarely carry more than a twenty dollar bill with us locally in Alberta but more when we travel across the country in the RV. Thunder Bay Ontario gas station had to pay cash when their system was down for a fuel fill of the RV a while back. Because we don't have to pay upfront for our gas we didn't know until after pumping $300 of fuel and went inside to pay
Also as a consideration, the dollar exchange right now is in your favour by 20%+/- so might not be a bad idea irrespective. If you don't use it all and the rate drops back to close to par ...........
Another thing here, we have all chipped and pins for our credit cards now so you might need to have one of those, although at markets some of the vendors use the square or on their cell phones and swipe our cards still I noticed. They won't do this for a $2 pop though!