A: I can't answer that question specifically for American Standard toilet. My toilet is a Gerber, but I believe that "round" is a standard size for toilets.
A: My seat is a perfect fit. It is solid and sturdy.
A: I was upset mine was broken
A: Most brands have three sizes (circular, standard oval and large oval) you just have to identify which one corresponds to you. The base of the toilets are standard, therefore if you choose the correct shape of any brand, it should fit without any difficulty.