There is a town called Makó in Hungary, so most people automatically assume that the saying refers to a geographical distance (which, by the way, is about 5000 miles, according to Google Maps, and includes tolls.) However, the saying does not refer to the town. Instead, it refers to a guy who also happened to be called Makó.
No, not that guy. Another guy.
Aaaanyhow, the story goes back to the age of the Crusades. Since attacking the Holy Land was an international pastime in Europe in the Middle Ages, obviously the Hungarian Kingdom could not pass up the opportunity to get in on the action. Our King András II recruited an army and set out in what was to be known as Crusade No. V (1217), and also as a very embarrassing disaster in the history of the crusades. We really didn't win any glory, and the campaign ended up being a very expensive tourist trip for our good king who eventually had to pawn his wife's crown to get back home. Ouch.
(András II is not one of our most popular kings.)
According to legend, Makó (or Chief Makó) was one of the soldiers in the Hungarian crusader army. Waking up from a drunken stupor on the deck of a ship one morning, he looked around and thought he was gazing at the walls of mighty Jerusalem. Turns out, they were still in Spalato (modern day Split, Croatia) and the army had not even left the port yet. And because soldiers are big on nicknames and hazing, the event soon gave birth to the widely known saying: "It is far off as Makó from Jerusalem."