Quantum Theory
In 1935, they came up with a theory for it. America was delighted, though he always felt a little sorry for the poor cat.
Whenever he was introduced to a new boss, he always had to prove that he was exactly what he claimed to be. It wasn't that they couldn't sense it in the most fundamental of ways, it was just that they needed some more logical convicing, and he believed that that was how a good boss should be, so he really didn't mind. Normally, it just took a simple trick.
Well, it was simple for him, anyway.
He would ask for a person, and one item that could be found on the person. He would ask that they be anywhere in America, but the further away, the better the effect. He would ask that the item could only be gotten from that singular person. And then he would bring it back.
Because he was America.
He'd never really thought about it before the 1900s. He'd just taken it as a given that he was everywhere at once, all the time, because he was America and everywhere that was America was America, so it figured that he (America) was everywhere. When he tried to explain it to his bosses, they always shook their heads and asked for either a drink or asprin.
And then there were times when he was asked to explain not why he was there, but why he wasn't, and those times usually hurt, but he couldn't be in more than one place at once. Once more, he'd found it so hard to explain. Even if he was everywhere, he could only be in one place at one time, if he needed to show up somewhere. If they didn't think it was an excuse, they thought it was just because he wasn't as omnipresent as he thought.
But it wasn't true. He was always everywhere: he just couldn't always be paying attention to everything. And when there were people looking at him, he had to be there for them to look at, so he couldn't be elsewhere at that time, even though he really was.
Then 1935 came about and all he had to do was to happy chirp that it was all quantum, and they left it at that. Even though he wasn't quite sure what exactly 'quantum' entailed, he figured that it wasn't really that important. If there was a chance that cat was still alive, it couldn't be all that bad.
Notes:
The cat refers to Schrodinger's cat, of course.
Personally, I believe that this applies to all the nations. And their reach is determined by their people.
Timeline: anywhen after 1935.