The British elite used to eliminate the opposition and exploit the conquered land, ergo the British Empire.
America sometimes does that, like with Iraq, but America often strives to create diaster zones as well, around Israel for example, and now with Pakistan and Afghanistan.
This helps the military/industrial American elite to perpetually suck the taxpayer dry in the interests of "making us safer" without ever actually "making us safer".
It's a lot like your local councils, but on a international strategic level.
Take money to "sort out the local traffic problem".
Totally fuck up the local traffic situation.
...demand more money to sort out the traffic problem...
...and so on and so forth...ad infinitum...
a job for life until the taxpayers get a braincell.