Assuming america = usa:
- America as we know it
- America as it relates to people
The first phrase translates roughly to "America in the form in which we know it (america)". The second phrase translates roughly to "America in the way in which it relates to people".
In phrase 1, the modifier "as we know it" concerns the state/form of an entity (America).
In phrase 2, the modifier "as it relates to people" concerns the activity of an entity (America).
Both phrases are supposed to be noun phrases denoting an entity. So, any modifiers should be about some static attribute (like state or form) of the entity, not some possible activity.
Hence, I am not comfortable with phrase 2.
On the other hand, this:
3 Sports as they relate to people
is okay, because sports are activities, so a modifier concerning the manner the activity is carried out makes sense.