There are some errors above.
Some stocks listed on the TSX do trade in US dollars. They often have a 'dot U' in their ticker to warn you. The newspaper listing also have a warning of some kind.
Your use of the term 'US stock' shows some confusion. That term is used to describe 'stocks that trade on US exchanges'. So a 'Cdn stock' would be one that trades on Cdn exchanges. So you would never say 'US stock on TSX'.
A number of companies are dual-listed. That means their shares trade on both US (in US dollars) and Cdn (in Loonies) exchanges.
When you buy a stock and specify the ticker as one from a US exchange, the deal will be done in US dollars. If you do the trade from within a Cdn dollar denominated broker's account, they will take the necessary Loonies, convert them to US dollars, charge you the conversion fee (1% to 2.5%), and use the US dollars to do the deal. That is what happens in RRSP accounts at all the brokers (except one).
For that reason owning US stocks within an RRSP is not optimal. Your transaction costs will badly impact your returns. Try to find a Cdn listed stock with the same exposure. Or keep your US purchases outside the RRSP in a US denominated account. You make only one FX transaction early in your life, and leave the cash in US dollars for the long-term.
The TSX has lots of non-Canadian companies. There are Chinese timber plantations, and US data providers, and African mines, etc. They may move their head office to Canada, or just create a sham Cdn presence, but their operations, and your FX exposure, is elsewhere.