I am a US citizen living in Berlin — which Bulgarian consulate handles my D visa?

You apply in Berlin. The rule is that a D visa application must be lodged at the Bulgarian embassy or consulate serving either your country of citizenship or the country where you legally reside long-term. Your German residence permit gives you the second option, so the embassy in Berlin is the correct and usually more convenient choice — no flight to the US needed. What you cannot do is apply from inside Bulgaria. The D visa must be obtained from abroad; entering visa-free for 90 days and trying to switch status in Sofia does not work for the standard routes, including the digital nomad one. The sequence is: D visa from the consulate abroad, travel to Bulgaria, then apply for the residence permit at the Migration Directorate. A practical note on consulate quirks: individual consulates genuinely differ. Some want extra documents beyond the legal minimum, some insist translations be done by translators they recognize, some want apostilles on documents others accept plain, and appointment availability varies wildly. Before you book, read the Berlin embassy's own D visa checklist rather than a generic list, and note that your criminal record certificate may be needed from both the US (FBI check) and Germany as your country of residence — this catches a lot of third-country applicants off guard. Both need apostilles and certified Bulgarian translations. Since you are considering the digital nomad route, check the income and documentation bar first — see /guides/bulgaria-digital-nomad-guide, and the general process in /guides/bulgaria-d-visa-guide.