The part where you say that 3rd world countries would be "better off" being spied upon by the US, in return for obtaining free WiFi! And it's not even a free choice to make.
The citizens are free to remain unconnected. The countries are free to build their own infrastructure.
Perhaps the choice isn't "free" because the incentives are too compelling, but that says something in itself about the benefits (even if we just assume the hypothetical risk of spying is real, as you did).
I'm assuming that the major risk with Loon is NSA "upstream collection" once you connect to it, and the danger of passive radio surveillance by Loon will be limited and/or duplicate capabilities which the US government already has. I could be certainly be wrong about that though.
The citizens are free to remain unconnected. The countries are free to build their own infrastructure.
Perhaps the choice isn't "free" because the incentives are too compelling, but that says something in itself about the benefits (even if we just assume the hypothetical risk of spying is real, as you did).