TL

R: I skipped this entire discussion because:
WE THE FUCKING PEOPLE ARE UTTER FAILURES
The imperial system is nothing more than an extension of conquest basis monarchy.
If you want to know why monarchy works, READ (PLEASE GOD READ) Aristotle. If you want to know why democracy (and Republic, by extension) are failures) FUCKING READ ARISTOTLE.
I hated Aristotle when I was 17. Then I grew up. I am now 37. Aristotle was a fucking genius.
Imperial systems are not failures. They are not great. They are recognition that conquest is a natural part of human society. Might is Right is a natural TENET of human society. There is nothing wrong with Conquest... so long as it incorporates the Conquered.
Right now, if America conquered Mexico and incorporated it into American society, with American protections and laws (and restrictions), eliminated the local drug warlords, instituted a national wage level and full-time benefits, and put a Wal-Mart and McDonalds on EVERY corner.... how many Mexicans do you think would complain with any serious-ness?
Conquest and Imperialism are natural. Don't try to pretend otherwise or you are deluding yourself.