If she cared, she'd make sure that kids who are from different cultures know about the common, shared culture in the United States.
When it comes time for those kids to go out into the world, they won't have any of the experiences that other Americans do. They will be seen as "other", because they will still be "other".
Like it or not, human nature makes us seek common experiences with new people. They won't be the first choices for new hires, and possibly not for promotions or educational opportunities.
She should not be allowed to be around children until she learns that her job is not to create a school-equivalent of Disney's It's A Small World. Her job is to make sure those children are educated to the best of her ability for success in the world.
What a hateful person - manipulating children's futures for her own idiotic reasons.
I used to have a huge amount of respect for teachers. Not any more................