As the title states which military had the better footwear, clothing and how easy were they to clean and maintain in any given climate? Soldiers with good clothing and footwear were generally more happy and less likely to face morale issues.
Best clothing - the US. Second best - Germany.
Best footwear - the US. Second best - England.
Not only is cleaning difficult (it’s hard to do when you’re getting shot at), but replacement is too. Getting clothes cleaned behind the lines is straightforward, but often makes them uncomfortable - with soaps that are, shall we say, primitive.
Ever walk in boots with holes in them through mud? Snow? Clothes get torn up pretty quickly in combat too, just from doing things very quickly and terrified.
The US had a huge clothing capacity, and ships to carry them. Even so, replacement clothing (especially boots - they rot fast when in water) was slow to arrive up front.
It’s a tossup between the US Army and the Commonwealth, with the Soviets having the best winter gear.
The US Army had multiple uniforms, one for each role. The Commonwealth had battledress which was one unform for most roles.
Battledress was incredibly influential. It was designed for motorized combat and marked a new wra of utility over custom in military uniforms.
The beret, a slightly later development, took over the heads of militaries everywhere, replacing the garrison cap.
The US Army’s combat uniforms were actually in flux for much of the war; they would’t settle until the M1951 Green pattern. The M1943 pattern was very modern and multi-layered. Most modern western combat uniforms draw heavy inspiration from it.
In terms of boots, both the US and Commonwealth had the same idea: low-cut ankle boots with gaiters/leggings/anklets. This saved on leather.
The Soviets had fantastic winter clothing: warm, hard-wearing and silent. They also had the practical gymnastorkya pullover uniform, dating to tsarist times in the 1880’s it started the trend to practical, utilitarian conbat uniforms. But the boots were terrible. Russian and Soviet boots are worn with foot cloths, not proper socks and it causes no end of foot problems. Due to the kack of fasters on the boot you have to pack the boot around the foot, which often leads to blisters.