Would an american doctor prescribe silver sulfadiazine to a 8yr old 2nd degree burn when antibiotics that dont slow healing are available?

Yes: This medication has been extensively studied and used in Shriner Burn Centers across the US. It is often used for both its germ killing effect and barrier abilities when dealing with an open wound. Its clinical success compared to alternatives has preserved its position as a treatment for more than 3 decades.

Ag sulphadiazine: Is often used to treat burns. It is also a good barrier cream. I am not aware of its reputation as a poor healing substance. All the best.