The USA and Canada are separate countries, with separate currencies and quite different exchange rates. It is important to remember the difference in exchange rates when comparing prices in the two countries. Although both the USA and Canada have Dollars and cents and the same denominations of coins, the designs of both banknotes and coins are different in the two different countries - banknotes are very different, coins only slightly different. American banknotes all have the same basic design, so you need to check the denomination very carefully when handling them.
Canadian banknotes have very different designs for different denominations.
I believe that higher denominations of notes are available but not in common use. I believe that higher denominations of notes are available but not in common use. It's a good idea to take a small amount of cash to start with, for example for road and bridge tolls. In both the USA and Canada travellers' cheques in the appropriate currency for each country are treated as cash in most retail outlets such as shops, restaurants, petrol stations, motels, etc., with reasonable amounts of change being given without any problems. No commission charge is ever made.