The thing is that the question was made by a friend of mine, and I thought it would be interesting to know the origins of the term and if it would be possible that a country turns to an empire nowadays.

We are from Spain and we haven't very clear if it could be possible, principally because Spain was once an empire but was dictated by a king with monarchy involved.

Not sure if its clear the doubt. Ask if needed.

Btw the historical info that you gave is amazing, thanks for the answer.