Riding the TTC and the presto app

I've seen some other threads but they are older. I'm in Toronto for the day. I want to use TTC. I've tried to download the presto app but I can't register as it only allows provinces (I'm from the US).

I've seen that I can just tap with a credit card. Is this true. What if I want a day pass? Do I need to get a card from a station, or is there a way to register the app from our of country?