"America has a far bigger GDP"
It depends on how you calculate it. According to PPP, China has a GDP of 25 trillion vs the US of 20 trillion[1]. Yes, China has a bigger market and bigger GDP. If you calculate nominal GDP, China has ~14 trillion vs the US 20 trillion. US is bigger nominally, but not far bigger.
PPP isn’t at all relevant in this discussion. People like to just bring up PPP like it’s magic, but it’s not. You have to understand the situations in which PPP is relevant and the situations in which it means nothing at all.
Moreover, you have to understand why PPP exists in the first place. Let me give you a hint: it has to do with arbitrage.
PPP doesn’t matter at all for a web company trying to make money from different countries. If a GDP is going to matter. It’s going to be the one based on an actual real number.
[1] https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(PPP)