Alienation is a concatenation of the words alien and nation, but with the grammatically correct replacement of the missing letter with an apostrophe callously omitted. Beyond the missing apostrophe, what makes it particularly confusing is that, in this case, alien refers to a now disused meaning of the word, i.e. a being from another planet. (Refer to the entry for alien to see the current common-use meaning)
Thus, alienation means a nation composed primarily of beings from another planet. Note that this does not necessarily mean a nation on another planet. If beings from another planet come to Earth and form a new nation or take over an existing nation, that would be considered to be an alienation even though it is on Earth.
There are no known nations on Earth that are composed solely or primarily of beings from other planets. Many politicians are thought to be unearthly, but that doesn’t necessarily make the nations they govern alienations. That would only be the case only if, along with its politicians, most of the nation’s citizens are also from out of this world.
Furthermore, no one on Earth has any proof, or even a hint, that there are any nations on other planets.
This lack of any known alienations is proof of the foresight of linguists (or whatever you call people who sit around all day, pick their noses and manufacture new words out of thin air). For them to have created the word before there is any known need for it is exceptionally forward-looking.