It's a reasonably common phenomenon that kids in bilingual families who are correctly raised tend to prefer the language of their country of residence (English, in case of USA).
Even if the parents teach them both English and the family birth language, and they are fluent in both equally, at some point they tend to start favoring English, unconsciously.
I have observed that some parents in this situation, as a way to enforce the bi-lingual development, refuse to respond, or do what is asked, if the child speaks to them in English instead of another language, until what was said is repeated in the "correct" language.
Are there any downsides to this approach?
Note: assume that the child is old enough AND fluent enough in both languages that this isn't a major hardship for them.
Note: The relative benefits or downsides of the goal of forcing the children to be bilingual are outside the scope of this question (it was somewhat covered here and here). Only a specific method of enforcing this goal is being asked about.