None of them. It's a constant battle. I always hear the trope that we "owe" China money because they buy bonds but the entire reason they're buying bonds is to keep the Renminbi weaker than the USD.
Germany is a weird corner case where the entire reason for the Euro is to allow them to keep their currency artificially weak by using the rest of Europe's economy as a place to dilute their export power. The DM was getting relentlessly stronger against the USD and Sterling and when the conversion to Euros happened, major holders of DMs got absolutely hosed.