Comment by jmyeet

The distinction between foreign and domestic is a legal one.

The Supreme Court has ruled that the US Constitution protects any persons physically present in the United States and its territories as well as any US citizens abroad.

So if you are a German national on US soil, you have, say, Fourth Amendment protections against unreasonable search and seizure. If you are a US citizen in Germany, you also have those rights. But a German citizen in Germany does not.

What this means in practice is that US 3-letter agencices have essentially been free to mass surveil people outside the United States. Historically these agencies have gotten around that by outsourcing their spying needs to 3 leter agencies in other countries (eg the NSA at one point might outsource spying on US citizens to GCHQ).