Well there haven't been any operations to retake the Cape of Good Hope or attempt to round the Strait of Magellan, and it seem to be Abyssal Seas beyond say Fiji to the Western Pacific and certainly the southern Indian Ocean. The South Atlantic is likely still infested since they've not tried to rescue Graf Spee yet.
North America's coast are kind of the question mark. Hawaii's been reclaimed, and I seem to recall something about a raid on California (might have been a different version of the game). But the Atlantic Ocean is sort of still infested, even with all the European ships and ports being liberated. So The American East Coast is likely having issues, or the American shipgirls are holding that for now.
Honestly, considering just how nice a lot of the Ido Abyssals are (AA Hime comes to mind) I'm not sure it's that bad...
A communique from Command.Good grief."The timing and method for your return to Japan is under consideration"And that's it....that taking a vacation is fine, right!?We got here free and easy, but the going back is all kinds of...W-Well, I guess it could be...?So anyway, that "waiting for orders" means..."All shipgirls are to proceed to Paris, and are to remain on standby after taking part in the ceremony, pending orders."What They Craveロンドンへようこそ!It seems the path that we painstakingly hacked out to advance has been cut to ribbons by the enemy forces.