Given the number of territorial changes that have occurred in and around Germany since the dissolution of the Holy Roman Empire, what do historians consider Germany?
What sparked my interest in this is the historic city of Königsberg which was apart of the German Empire until after the Second World War when it was taken by the Soviets and renamed Kaliningrad. Many famous Germans such as Immanuel Kant were born there and I have a hard time considering it as "Russian". Just wondering what other people think.
Königsberg, of course, was German, or at least Prussian - it is Kaliningrad that is Russian. There was no state of Germany until 1871, when unification was led by the Prussian Otto von Bismarck. Immanuel Kant was born in Königsberg in the Kingdom of Prussia. Someone like Alexei Leonev, conversely, lived in Kaliningrad after the war due to Soviet settlement efforts.
There are many other former German cities - Stolp, Wałbrzych, Wrocław, Dorpat - that when spoken of now would not be considered German. A more famous case is Prague, which in the early 19th century had a majority German-speaking population, but was culturally Bohemian (concerted Czech nationalist efforts following the revolutions of 1848 would significantly complicate this later).
An antecedent to the German Empire is the German Confederation, established at the Congress of Vienna. The Bund, led by Austria, was weak for a variety of reasons, but included many states we don’t recognize today as “Germany”: the most populous member was the Austrian Empire, while modern-day Luxembourg and Lichtenstein, portions of Poland, Belgium, Tirolian Italy, Schleswig, and so on. The Holy Roman Empire, as you allude, had even more expansive borders, though by 1806 it had shrunk considerably. And these are not considered “Germany” even though the residents (often) spoke German.
There is great difficulty particularly in the case of Germany in ascribing a general national identity to pre-unification states or free cities. Germany has a particular regional disposition given the relative recency of regional autonomy and a rather wide cultural gulf across the state - a resident of Würzburg might consider themselves Bavarian Franconian before they are German. (edited - thanks to /u/ririkkaru)
So answering “where is Germany” is very dependent on the time you’re looking at and who answers you. Outside the direct influence of Germanic states, German speakers were distributed quite widely, with the Baltendeutsche in Estonia and Latvia, the Wolgadeutsche in southern Russia, and the Ukrainian Schwarzmeerdeutsche. John Connelly’s From Peoples into Nations: A History of Eastern Europe, Jeremy King’s Budweisers into Czechs and Germans and Anthony Bushell’s Polemical Austria come to mind exploring these questions.