A quick review of the last 200 years indicates that Western nations have to project power to fight and keep "the enemy" at a distance. We can't walk away from Afghanistan for the 3rd time, if we do I think the bugg*rs might chase us back to the UK.
Iraq always was about the oil, unfortunately our colonial friends where under the misapprehension that something approaching democracy could be achieved. Hah! The Brits knew otherwise in the 1920s.