I'll try and answer this for you and touch on some other points...
Basically, in a sense we are currently in the 'petroleum era', we use oil for fueling our cars, planes, ships, tanks and lawnmowers. Also, remember
that most of our every day comsumer crap is derived from oil such as plastics, pharmaceuticals, fertilisers - we use oil for everything!
Like Odium said, during 'The Boom' in America when the petroleum era was just beginning, people never imagined that oil would ever run out and there
was so much of it, so you get this whole 'American way of life' culture:
- You've got urban suburbia's, everyone lives miles away from their workplace and commutes everyday in their ridiculously huge cars!
- Nothing is recycled, everything is thrown away, nothing is repaired, etc.
- You get the idea...
Everyone took the oil for granted and it wasn't until during the second world war that Roosevelt and his advisors thought there was a crisis - they
had to supply oil to all the allies to fuel the war as well as supplying America. The oil fields were beginning to run dry, oil became a national
security matter as America would have to be become dependent on foreign oil reserves - this is not ideal in the slightest.
Now, this is why America has strong ties with Saudi Arabia - they need the oil. In the 70's and 80's they traded weapons and technology for the
promise that they would have access to Saudi oil fields. As you know today, America still has strong ties with the middle east which incidentally
harbours the world's greatest known oil reserves (as well as possibly Bin Laden).
however now we have a problem:
- America obviously has an increasing demand for oil - an increasing population, more cars, more industry, more everything.
- America's oil reserves are dangerously low (apparently).
- America has few friends, they have to import oil from 'unfriendly' countries, hence the whole 'war on terror' rubbish. Now because of this
America is destabilizing the middle east region despite every effort to keep it stable, as stability is in their interest - there is more chance of an
interupted oil supply in times of conflict.
- There is increasing demand for oil imports from other industrialising nations such as China and India - this increases the competition for the
world's remaining oil reserves which everyone else wants.
- There are also various political and economic complications such as keeping the stock market stable which currently prevent a transition away from
petroleum dependence. Also, no-one cares about it at the moment
So that's it really, the success of America is tied directly to an uninterupted supply of petroleum which is projected to 'run out' shortly.