The "Made in USA" were wide-distributed in the 1950s and were used by many doll companies. Roberta used this doll, DeSota, Valentine, Horsman, as well as many other companies.  They have both open and closed mouths.  They are most often 14 inches.  They vary widely in the quality. These dolls were made by a major manufacturer and sold to other companies.  Here is a general guide to determine the overall quality. This is not to say one is better than another, but will help to identify who the doll is:

The Hard Plastic:  The quality of the lower-end "budget" doll will be considerably lighter than the higher-end dolls. The plastic has more of a translucent look. 

Seams: The biggest indicator of who the "Made in USA" doll is will be the "seams."  The higher-end dolls will have smooth seams.  The "budget" dolls will have seams that are clearly indicated. You can see the seams in the arms, and the legs, and other joints as well.  This is a tell-all sign. The more crude the seams, the more "budget" the doll is.

Walker Joints:  For walker dolls, the mechanism is also a "tell-tale" sign.  Look at the pin. 

Unpainted or painted rivet: You can actually see the pin at the upper leg. It will be visible as a round rivit at the top of the leg.  Most Sayco dolls, Made in USA dolls, Imperial, and Eegee used this rivit.  They will usually be a higher end doll.

Painted countersunk-type screw: This screw is actually in the plastic.  You can see it as a raised area at the top of the leg. Most of the Horsman dolls, and a few Sayco dolls used this type of screw.  They are generally a higher-end doll in the Made-in-USA category.

Hidden pin: The pin is inside and is hidden - it will appear as a bar going from the each leg and through the torso.  The hidden pin dolls are generally the less-expensive "budget" dolls.  Interestingly, these dolls are great head-turning walkers -- move their legs and their heads will move quickly.

I hope this helps -- and Happy Doll Hunting!