Why do Americans keep on losing wars at the same time engaged in mass scale slaughtering of civilians in the soils they invade?

This article in The Telegraph speaks volumes as to why the USA, the most powerful military ever existed in the planet keep on losing wars in the countries that they invade while at the same time indiscriminately slaughtering the incent civilians in the invaded countries. As per this article the US spends £12.5 billion a year on air conditions in Iraq and Afghanistan. 

USA armed forces' reluctance to relinquish the comfortable lifestyles which they enjoy back at home in the invaded soils too while relying on too much in technology, again as measure not to risk their lives and limbs, have cost dearly innocent civilians in the invaded countries. Numerous drone attacks that slaughter civilians in thousands in Afghanistan are case in point.  The particular article in The Telegraph goes on to say that

 'The US military spends about $20 billion (£12.5 billion) a year just to air-condition its bases in Iraq and Afghanistan, a retired senior officer has claimed. The Brigadier General Steve Anderson, who served as chief logistician to General David Petraeus in Iraq, said that the American department of defence (DOD) was shockingly inefficient in its energy use.

"In essence what we're doing is we're air conditioning the desert over there in Afghanistan, Iraq and other places," Brig. Gen. Anderson said. Taking into account raw fuel, transport and security, "DOD will spend about $20 billion annually to air-condition tents and temporary structures,"

he told National Public Radio. Brig. Gen. Anderson explained that the fuel used to power air conditioners in remote bases in Afghanistan is shipped into Pakistan, before being transported by land for more than two weeks. It must cross 800 miles of roads, many little more than "improved goat trails", and areas where insurgents will use roadside bombs to target troops serving the US war effort.

Brig. Gen. Anderson claims billions of dollars could be saved if the US military used simple energy-efficient techniques, such as spraying tents with common insulation foam used in domestic roofs.

 In contrast a Sri Lankan armed forces' soldier defeated the most ruthless terrorist origination in the world, claimed by none other than FBI itself, with perhaps one tenth of facilities and comforts that his counterpart in the US forces' has access to.  SL forces risked their lives and limbs to minimize the civilian casualties not relying on methods that harm the lives of the civilians. And also they faced a foe perhaps 10 times formidable and comprising of 100 times more suicide carders than what the US faces now. Yet SL forces saved 300,000 civilians that terrorists used as a protective shield for their survival. Would the USA have ever undertaken such a feat?

As I pointed out in one of my previous articles the spectacular success achieved by the Sri Lankan armed forces is too much to the USA and the West to digest.  So Sri Lanka has to pay the price for doing what the most formidable military powers that ever existed in the world can't do.