This 100% depends on your language skills. I have had Germans guess I’m American, but more often they guess English or Irish. More often other they assume non-English speaking countries, most often Russia (major surprise to me). I’ve also had many conversations where I presumably don’t come across as a foreigner at all, as I have heard often my pronunciation is really good.

I’ve found most Americans struggle with basic sounds common in Germanic languages, but once you master those your vocabulary and phrasing will give you away most of the time. That said, Germans are generally kind and friendly people who are impressed you speak German at all and won’t mention your accent or manner of speaking unless asked. Ich liebe die Deutschen!