I am not sure what you mean by huge squad and platoon. In WWI, the squad was only eight men as compared to the triangular formations as mentioned above. In WWII triangular formation, the US Army was built around an 11 man squad. Yes, the divisions did shrink as they lost an infantry regiment, but this does not fit in with smaller echeloned commands associated with 15-28mm gaming scales.
As a side note, the French squad/platoon/company structure of 1918 was amazingly similar to the US WWII era 11 man squad. I don't have my notes here with me, but if I remeber correctly it was 10 men including: a two man chauchat team; three man rife grenade team; 4 man maneuver element; and of course a squad leader. Truly revolutionary!
As far as tactics between the wars, the US infantry had the same drills and formations. Don't be confused with trench warfare thrown in there as this was non-standard to the drill manuals of the day. Entire separate books cover these tactics, and were often either French translations, or by Commonwealth authors. I have a decent sized library of manuals ranging from 1912-1945 (again not here in Korea with me :-/) and love talking on this subject. :-)