Further quibbles:
all lodging and meals (ever check London hotel prices in summer, gang?)
But it can be done more cheaply overall by lodging outside London and commuting in.
a tour of the House of Commons (can’t get that as an ordinary tourist)
Yes, you can, during part of the summer recess. See House of Commons Tours.
Not wanting to seem stupid or anything, but doesn’t the noble ideals of this organisation seem to translate into rather one-sided travel? All those specially invited “delegates” venturing out into the world from the US, but absolutely none the other way. I always thought of “ambassadors” as being an international reciprocal arrangement.
If I was being really cynical I might suggest that the “People to People Student Ambassador program” has no real international presence and is just a commercial American travel company.
Not that those especially “selected” won’t have an exciting experience and holiday (for the money you’d certainly hope so), but all the rest of it looks very much like inflated dressing to make it appear something it’s not.