I Am A Real Werewolf

Google translate did a good job. I had no problems understanding you. I've never heard of an empire ruled by werewolves or the like, but I don't know everything. As for why werewolves went underground, I would argue that it was primarily because of the spread of Christianity across Europe. After the fall of the Roman Empire, a lot of things fell apart. Non-believers were ostracized, if not killed, and werewolves were basically disallowed from being Christian. There were a few exceptions of, for example, werewolves interacting with saints (see the "Werewolves of Ossory"), but it was generally a dangerous time for anyone who was "different". Early on, there were plenty of battles, but it became clear that the best thing to do was hide. A lot of history, even physical statues, were destroyed to erase "pagan beliefs". With it went a lot of werewolf history, you can be sure. Despite that, a lot still persists, although it's almost entirely through a Christian lens throughout most of Europeans history. The most popular accounts you'll hear of are serial killers who were supposed werewolves (Stubbe, Garnier, Roulet, Verdun, Grenier, etc.). Some may have been, but then you're just talking about a minority composed of psychopaths. Meanwhile, most werewolves stayed quiet. As for the next question, there were tribes and certainly places where werewolves lived in great numbers. It wasn't really relevant to have a "country" for werewolves. Even well after the fall of the Roman Empire, you might still find villages full of werewolves, but it was rare. Honestly, it's difficult to find a lot of useful information. I've spent years studying the subject, and I can only manage to find pieces here and there. Some you can't even find on the internet at all anymore. Some you have to find in rare copies of books at libraries that have a rare books section (especially at universities). Here's a good list to get you started: the Benandanti (or "good walkers"), Bisclavret, the Gandillon family, Vseslav of Polotsk, Damarchus, the Antacus family of Arcadia, the Wulver, Demenebus Parrasius, Baianus of the Bulgarians, Moeris (Virgil), King Lycaon (Ovid), the werewolf of Padua (Job Fincel), werewolves of Scythia (Herodotus), and Cynocephali ("dog-headed" people).

No. Werewolves were always a minority which was shunned, ostracized, and feared. They never ruled anything unless they were some kind of nobility to begin with.

You “real werewolves” don’t seem to have much of a grasp on history.

While they didn't rule them, Lycans and other shifters (mostly wolves) used to be more common in Native and First nation tribes.
Quileute tribes mostly (no not like Twilight 😒). We even have a legend about it.