It was China. My experience spending about a month in China this summer was that Uber charged my (US issued) card in USD, but the exchange rate was identical to the pegged rate after I checked it (No DCC). This USD charge was actually helpful because with the Capital One Quicksilver, I get an effective 21.5% back on USD-denominated Uber transactions, making Uber perhaps the one merchant where a DCC surcharge could actually enable you to get out quite a bit ahead.