I would have to go through my calendar notebooks to get an exact number of days I have been in Germany since 1971. Living there for a duration of time, no, that I've not done. That is the main difference here. Of course, the Germans knew/know I was/am a visitor.
In the early 1970s they thought sometimes if I wasn't a tourist, then I had to be an exchange student studying at a German university. But there have been a few times, 3 come to mind immediately, where "they" thought in asking me for directions, say in Berlin, or elsewhere, or getting into a conversation, sometimes started by them, other times started by me, where " they" assumed I was living in Germany.
No doubt they know I am outsider, My friend living/working in Austria as an ex-pat has told me likewise, and he is fluent in German. Being tagged as an outsider, I expect that, almost always now I tell them I'm from Calif. They recognise that by one's German, ie, the accent, fluency, choice of vocabulary, pronunciation , my clothing style too, etc.
I do likewise too, can spot out immediately Americans speaking German that something will give that away, be it accent, (which usually is the case), fluency, intonation, their use of the definite article, ie getting them mixed up, use of idioms and expressions, diction, listening for certain sounds, and so on.
If a German is from Stuttgart, and the other one is , say from Bonn, or Hannover, Magdeburg, I'll point out the one from Stuttgart after a minute or two conversing with him.
On learning a foreign language, eg, specifically as it pertains to German here, "make sure you're doing it for the right reasons."
I dissent from that view, totally disagree with that. I have never said such a thing to any prospective student of the language, and would certainly not give such advice to someone nowadays of post-college age entertaining the idea of wanting to take up German. Not the way I see it at all....we can agree to disagree on that topic.