Lyndon Johnson is a bit different case though
Correct me if I'm wrong, as I do not have great knowledge of American history, but I do not recall him spending lifelong work to turn Texas from indebted state into one of the richest states of the US, nor do I recall him giving Texas any privilegia, and I do not know about him moving capital of the US and the American government to Austin, either. Nor has Texas been the core of the country he had any but nominal power over as the President of the United States of America.
Charles IV on the other hand did spend lifelong work to build a strong Kingdom of Bohemia from the ruin left him by his father, moved the Imperial capital to Prague, gave Prague even more power within the Holy Roman Empire, and Bohemia did form the core of the lands he personally ruled as the Emperor of the Holy Roman Empire. He may have had nice titles he gained with becoming the Holy Roman Emperor like King of Germany and King of Italy, but those were mere honorific titles, and he never ruled these personally, as, as you might know, Germany and Italy were broken into tiny states with their own rulers. What belonged to him were the rather small Duchy of Luxembourg (home of the House of Luxembourg he belonged to - and no, before pointing that he was not a Czech, him of being of Luxembourgian origin does not stop me from wanting him as leader of Bohemia when we can have Catherine the Great, who was of German origin, as a popular leader choice of Russia), Kingdom of Bohemia, Margraviate of Moravia, Silesia, Lausitz (and later purchased Duchy of Brandenburg), which were all collectively known as Lands of the Bohemian Crown, ergo, belonged under the rule of King of Bohemia and were parts of Kingdom of Bohemia. Do not mistake this Bohemia (bold red), a part of the lands ruled by the King of Bohemia...
...and this Bohemia (everything in green)...
...because I'm talking about Bohemia being the latter, the lands being crown lands, belonging to the Crown of St. Wenceslaus, under direct rule of King of Bohemia.
So, again, I ask, what Civ would you give Charles IV? Holy Roman Empire, which was no Civ at all by Charles IV's reign with its hunderds of semi-independent leaders who fought each other, Luxembourg, which was merely where his house came from, or Bohemia, which formed the absolute majority of the lands he ruled, which he sought to expand and improve, and on which he focused most of his rule? Because we're talking leaders as leaders of Civs, respectively.
So far, you're the only person from this great majority of the world you're talking about that I've ever heard being actively opposed to adding Charles IV as the leader of Bohemia for Civ game.