This is a rundown of the 20mm plastic figures for the USA during world war two. I use these little beauties myself and have since the early 60's when I discovered Airfix in a hobby store in Burbank, CA. The process of painting them has not changed a lot. WASH them!! Then I spray them with a clear plastic such as Red Devil Polyurethane. This stiffens them. At this point they can be painted, but I find the paint sticks better if you either spray them with primer (black works well), or better, prime them with Latex Primer. I have a pint jar I bought at my local Ace Hardware that I have been using for years. The latex primer dries stretchy and doesn't crack when bent. I use it thinned, and brush it on with a stiff brush. You can paint over this or stain with black paint first. A clear spray goes over the final paint job. I have also tried etching the figures with vinegar for 12 hours or so, then skipping the clear plastic. I think it works, but find I go back to the above method.

But on to the figures. My personal preference is for figures advancing or firing, preferably in standing positions. I base them for CD, and Clash of Armor, and use them as is for Spear Head. I will use prone figures for dug in troops, and deployed MG. The reviews are based on what I have in my army, or waiting to paint. I used several boxes of ESCI US Amny, and my count on them may be off +/- one figure on rifle or SMG.

Airfix USMC. This is still available, and still a good buy. They have been updated since my first box back around 1965, and still look as good as any other. They and the Matchbox are slightly smaller than ESCI and Revell. These are definitely USMC, rolled sleeves, helmet covers, and you can almost see the herring bone twill the fatigues are made of The rifles are one of the better M1 Garands, and the M1carbines are well done also.

There are 46 pieces, and they break down as follows

Rifle-14, Carbine-12, SMG-5, LMG (prone)-2, Bazooka-2, leaders-no specific pieces, but four of the carbine, and one of the SMG would make good officers.. There are also 8 prone figures and a raft and two man crew. Unfortunately no mortars.

Airfix US paratroops.

Matchbox US Army

Revell U.S. Army

Airfix Anzak. An old set that is great for the pacific or north Africa. Seldom mentioned the Anzak made up a large part of McArthurs forces in the pacific. Unfortunately no MMG or mortars are in the set, but several figures sitting on the ground can be turned into mortar crew. There are also figures carrying boxes useful as moving weapon crews or artillery crew, or ever bearers.
Rifles-16, SMG-6, Kneeling Bren guns-4, prone Bren guns-3 officer-1, radio-1.

Revell Anzak. You can't have too many of a good army. Actually my Revell Anzak were painted as South African's for North Africa. They are larger than the Airfix, and about half have helmet rather than the Aussie hat. There are four ammo carriers that I use for the second man on the Bren gun crew. Again no mortar.
Rifle-16, SMG-8, Bren gun (kneeling)-4, officer-2, radio-1, MMG-3.

Aiffix Gurka. This is a nice set, well worth having as a British player. The Gurka were used in both the Pacific and Europe, and were feared by their opponents. Rifle-23, SMG-3, officer-1, Bren gun( advancing)-3, knife armed-7.

Atlantic Indian Brigade. These may no longer be available, but if you see them, grab them. They are in shorts, turban, and have the MkV Enfield "jungle carbine". Several have swords. They are large mean looking troops and fought in the Pacific, North Africa, and Europe.
Rifle-20, SMG-3, officer-4, MMG-3, swords only-3.

Related

WWII German Plastic Troops
WWII British Plastic Troops