Because we think we are still a superpower.
You heard the famous dictum “those who ignore history are doomed to repeat it”?
History tells us ancient empires met their demise by over-extending their military in foreign lands.
Latest example is Hitler’s Germany sending military deep inside Russia.
Here is the sad truth, no one can be a superpower with debt bigger than GDP. Currently our national debt is 35% bigger than GDP.
Not really. I mean, you wouldn't have an empire in the first place unless you sent your troops to foreign lands, right? Arguing that the Roman empire fell it didn't keep its armies in Latium kind of misses the point.
I would argue that most empires fell because the values that gave them the strength to build the empire withered away when life got too easy with imperial wealth.
The people got soft, so the empire fell. That's the far more common story. That's at least if we're talking about the classic definition of an empire - one that lasts more than just a decade or two.