I've already posted one proposal for new US Army uniforms, but after much thought, revision, rethought, and re-revision, I've come up with a more comprehensive, aesthetically pleasing, and plausible proposal. The inspiration for the different uniforms comes from various eras of US Army uniforms.
The ceremonial uniforms are similar to the current US Army ceremonial uniforms, with the addition of a standing collar, a gold waist sash, a shako, gold metal epaulettes, white trousers for the parade uniform, and new overcoats. The white trousers and shako are inspired by the West Point parade uniform, and the gold metal epaulettes are inspired by American Civil War era parade uniforms. The insignia worn on the shakos are two crossed rifles. The new overcoats are inspired by Civil War and Post Civil War era frock coats.
The service uniforms are inspired by WWII era American uniforms, modernized for the 21st century. I have also tried to cut down on the number of medals, pins, rank markings, and other flashy, unnecessary, and overdone paraphernalia that is worn with the current ASU. The plumed hats that are worn with the more formal versions of the ASU Cl. A uniforms are inspired by the hats worn by some Civil War era infantry units such as the famous Wisconsin Iron Brigade. The insignia on these are two crossed rifles.
First line: Army Ceremonial and Parade Uniform (ACePU)
Second line: Army Service Uniform Class A (ASU Cl. A)
Third line: Army Service Uniform Class B (ASU Cl. B)
Fourth line: first four uniforms - Army Service Uniform Class C (ASU Cl. C); last three uniforms - Army Combat Uniform (ACU)
*All uniforms shown are for non-commissioned officers. The differences between the ranks are practically only reflected in the rank markings, with a few other minor changes.
*The medals shown are completely random combinations of colors. They're pretty generic colors though, so chances are they resemble some real medal or another, but that was not my intention.
*Credit to Glorfindel for the combat uniforms (I only added different boots and a belt), for the winter jacket of the ASU Cl. B and C (I only recolored), for the rain overcoats of the ACePU and ASU Cl. A (I only recolored), and for the plumed hats (I only recolored the plumes).