Nostradamus was of French-Jewish background and spent his life in France and Italy. If he invented his prophecies himself then you could imagine that they would relate to his own known world. In that case he should be regarded, as some sort of science fiction writer with ideas on how the future might look like (similar to Jules Verne, Heinlein and other SF writers). If such is the case we should be able to find correlations between his prophetic quatrains and his own known world, his experiences, knowledge, expertise etc. The core of his work should then include elements that relate to his city, his own background and environment, France, its politics and economy and the like. It would be less likely that Nostradamus would have created predictions about countries that he did not have intimate knowledge of, did not visit or which he did not even know of.
If Nostradamus really received a large number of clear prophecies from an occult source, he could have easily made a sub selection, limiting himself to themes that he found interesting. Therefore you might still presume that although the resulting quatrains are extremely difficult to interpret, they might deal with writer related issues only.
Then it all depends on the occult source what events might have been selected. If we believe that there really was an occult source that gave prophecy to Nostradamus, then it would depend on the interest, motivation and intention of this source to what events, geographical area, themes etc, the quatrains relate to.
Since we cannot repeat what Nostradamus made us believe he managed to do, it could possibly have been the product of his own fantasy.