Because Judah is not fictional. It’s historical, which would make someone think they are reading an alt history or something. It just wouldn’t be a good choice for a writer or screenwriter. It would be like having a “fictional” country called the Confederate States of America. There’s a lot of history that goes with that and so readers will have expectations about why the author chose that name.
Hebrewvania? Yehudinesia?
Here are a couple of fictitious maps which featured prominently in the Three Stooges short subjects You Nazty Spy! and Malice in the Palace.
On my bookshelf is a rather well-done parody of a travel guide to Molvanîa: Land Untouched by Modern Dentistry.
They did a whole series of them.
How about the granddaddy of them all, Ruritania, from Anthony Hope’s 1890s Prisoner of Zenda and its sequels:
“Hope’s novels resulted in “Ruritania” becoming a generic term for any small, imaginary, Victorian or Edwardian Era, European kingdom used as the setting for romance, intrigue and the plots of adventure novels. It lent its name to a whole genre of writing, the Ruritanian romance”
“Later authors developed the idea further. Ruritania inspired other fictional countries, such as Ixania in Eric Ambler’s The Dark Frontier, Riechtenburg in Dornford Yates’ Blood Royal and Fire Below, and Evallonia in John Buchan’s Castle Gay and The House of the Four Winds”
I just saw a 2017 film, “A Christmas Prince”, set in “Aldovia”, which reminded me of Ruritania.
Hurrah, Australian comedy represent! The Working Dog / D-Generation guys made that.
Dont let’s forget the happy vaguely-European states of Guilder and Florin
I’m not sure I’d recommend extending the principle to an Israelish nation of Shekel though. And as for Canada…
At Wossamotta U in Frostbite Falls, Minnesota, a classmate from Moosylvania told me about some east European country named Pottsylvania.
[Old, old Jewish joke] Why don’t they just call it “Irving”?
Why did he do that? How is a fake state integral to the story?
It makes sense though, in that it fits the pattern of the actual Jewish nation’s name - they resurrected the name “Israel” from the historical Kingdom that existed at the same time.
OK, but this makes it a worse idea for a fake name, not a better one. Just about the only fake name for Israel that would be even worse than your suggestion would be “Israel”. 
Why?
The idea is to look to the real name, see what sort of thing it is based on, then choose something similar - as people are doing with the names for US states.
“Israel” is based on resurrecting the name of an actual Jewish nation from the past. So, why not resurrect another actual Jewish nation from the past?
West Palestine.
Or maybe East Palestine.
English speaking countries can be created by just appending “New” to a place in England. New Wales, there, we’ve created one.
Fr a Scandinavian country, throw a “Mark” on the end of some random phoneme, like “Tussmark.”
“Aramia,” “Tel Ammon” and other stuff like that works for a Jewish country. Take a name that actually exists in Israel and mix it up a little.
I’m disappointed. I thought this would be the wonderful song about driving in Massachusetts as featured on Car Talk. sigh I don’t see it on the Youtubes.
Is Fremont anywhere near Jefferson? :dubious:
There have also been attempts by the upper peninsula of Michigan to obtain statehood. It would be called Superior.
Designated Survivior came up with some bizzarely creative names for fictional countries. North and South Korea became East and West Something-or-other.
The Transformers cartoon had a Middle Eastern country called “Carbombya”.
Hyuk hyuk