ARM delisted in 2016 because they were bought by SoftBank and became private company. The fact they (and the others listing in US) are not going to EU tells you a lot, they view it lower than London.
Helmand/Afghanistan was an insurgency war. IEDs, bombs under the road, shoot and scoot. The Taliban would run rather than take on NATO troops head-on. The US also failed, doesn't mean the US cannot handle a conventional war because of Afghanistan.