Two decades ago, female American troops in Saudi Arabia were pressured to keep their sleeves rolled down and wear headscarves when off duty. This caused a stir back home, and hurt morale in the military. The unofficial policy (of ordering women in Saudi Arabia to dress as modestly as possible) continued until a decade ago, when some military women sued the Department of Defense, and Congress banned such dress codes for American military women in Saudi Arabia.
But at the same time this was happening, the same kinds of rules were being applied in Afghanistan. While some female soldiers and marines appreciate the possible "hearts and minds" angle when they accompany patrols into villages so they can speak with the local women (something male soldiers cannot do, at least not without angering the local men), many see scarves under their helmets as foolish and craven. The Afghans know the Americans have female troops, who are armed and can fight. Why try to pretend that these women are anything like the women in the villages being visited. The Afghan women, especially the young girls, admire these foreign warrior women just as they are.
For now, the headscarf policy is still applied in some areas, and the female troops put up with it. But it does little for morale, and is not certain to have the desired effect on male, or female, Afghans.