In a way, this is true at any point in history, once an empire gets too big for its own good, it begins to fall. The only thing that can prevent this is having generation after generation of hard working courageous people who arent tempted by the vast wealth that is accrued by such an empire. And that is asking a bit too much of human nature .
The idea of forming a new RE isnt a new one. Remember the "Holy Roman Empire"? The was fairly succesful for a while IIRC. Mussolini tried to re-establish the RE by allying with the Nazis inWWII. He came close to succeding, but Germany wasnt able to subdue England in time so they lost Africa, and then Italy, including Rome itself.
I think that if any modern nation could start a new RE it would be the US. Militarily we out gun everybody else and economically were better off than the Romans ever were. But we dont have the attitude that we have a dvine destiny which the Romans held. Plus if it werent for imigration our population would be stagnant or declining. All in all I think it would meet with great success early on but it wouldnt last, and the benefits we would get from controlling and empire wouldnt outweigh the cost of maintaining one. Therefore, lets leave the RE where it is, dead