oil...?

F*cking nothing

A bigger budget for the military industrial complex which directly and indirectly provides millions of jobs with taxpayer money. Biggest social welfare scheme in history, albeit a very inefficient one.
It's time for another war, since those damn socialist pigs are trying to cut the defense budget again.
http://tech.fortune.cnn.com/2014/01/17/budget-deal-a-win-for-defense-contractors/
A trillion dollar budget is way too low!

Erosion of liberty and more countries that are burnt to the ground and hate you?!

This kind of thinking and loss of respect around the world. Check out this movie and well many others. http://www.imdb.com/title/tt2532528/ (Dirty Wars)

America is not an anthropomorphic entity. Individuals within the United States benefitted from these wars, while other individuals were affected neutrally, while other individuals were affected negatively. "America" describes the collection of individuals contained within this region. Only collectivists believe populations are anthropomorphic entities, but observation alone is enough to realize this is not true.

When the alternative is imperialism, isolationism seems quite pleasant; however, there is a third option: free association of individuals, and stop threatening them with force for associating freely with whomever they wish to, i.e non-interventionism. If I want to trade with somebody from China, I shouldn't be hindered by any one person or a collection of persons who have no business with me. This means no tariffs, and no barriers. An isolationist would approve of tariffs and barriers for that purpose alone, while an imperialist would pick and choose which barriers benefit him/her. 

The common american, got less money to actual public services (education, social security etc), the manufactures of everything us military arms and supplies got a lot. Its a multi-trillion dolar industry.

Americans have been fed so much propaganda by both parties, that they actually believe their wars exist for "freedom". War never changes, , war is and always will be about power.

I think you have the wrong idea about wars. The past time the US "got something" out of one was probably 1898, and we promptly lost it. In fact, we've lost a lot more than we've gained during all of our wars, even the ones we "won."