ik978,
With the choice in the US you can get cotton and "cotton rich" shirts, which are far more comfortable to wear than the cotton/polyester type materials in most uniform shirts I have seen here.
The quality of the US shirts is also generally good (ain't competition wonderful) , and the nominal sizes are "real", not based on emaciated Indians ---- as in the new sizes in may Australian stores, where the old 3XL is now 7XL.
Tootle pip!!