Re:
God save the Queen.
Not being British, I really don't know what it means for God to save the Queen. Perhaps Red or Tdol can answer that one.
Certain verbs and prepositions tend to go together. Native speakers rarely think about why that is. (It might give them headaches.) Thus, they have difficulty explaining it. When a person wants a specific action performed by another person he will
ask that prson
to do that action. The words
ask and
to are paired with great frequency. (I will leave any additional explanation up to Cas.)