Even with a CPF, the document needed (which isn't excessively hard to get if you're a foreigner in Brazil), there's another problem...using a US card to pay. Unless they've changed their ways in the last few years it's still near impossible to pay on any Brazilian airline site or any Kayak-like site in Brazil with an American debit card with Visa or Mastercard symbol.
Last time I had to book at SDU (Rio airport), I needed to take most of my day to go to the airport, wait in long lines and buy the ticket physically, with cash or (get this) by card! This was a 5-6h process including public transport (and I actually lived 10m away by car at the time).
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At the risk of getting too off-topic (which I may have already done above), here's another recent public transport problem, when bus drivers went on strike in Sao Paulo, this is what happened on the metro. https://www.youtube.com/watch?v=CXycKeyDKXk
Last time I had to book at SDU (Rio airport), I needed to take most of my day to go to the airport, wait in long lines and buy the ticket physically, with cash or (get this) by card! This was a 5-6h process including public transport (and I actually lived 10m away by car at the time).
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At the risk of getting too off-topic (which I may have already done above), here's another recent public transport problem, when bus drivers went on strike in Sao Paulo, this is what happened on the metro. https://www.youtube.com/watch?v=CXycKeyDKXk