Where does calling Heaven "My True Country" come from? I was reading C.S. Lewis' Mere Christianity yesterday; in the chapter on Hope, Lewis refers to Heaven and his "True Country".  Perhaps it's a coincidence, but there's a Newsboys song with that as a lyric.  Is that a Biblical reference or does it start with C.S. Lewis or is it just a Protestant meme?
I am not sure, but it may be a reference to Hebrews 11:


  13 All these people were still living by faith when they died. They
  did not receive the things promised; they only saw them and welcomed
  them from a distance, admitting that they were foreigners and
  strangers on earth. 14 People who say such things show that they are
  looking for a country of their own. 15 If they had been thinking of
  the country they had left, they would have had opportunity to return.
  16 Instead, they were longing for a better country—a heavenly one.
  Therefore God is not ashamed to be called their God, for he has
  prepared a city for them.


Also, Philippians 3:


  20 But our citizenship is in heaven. And we eagerly await a Savior
  from there, the Lord Jesus Christ, 21 who, by the power that enables
  him to bring everything under his control, will transform our lowly
  bodies so that they will be like his glorious body.


For reference, I believe this is the C. S. Lewis quote you are referring to:


  “The Christian says, 'Creatures are not born with desires unless
  satisfaction for those desires exists. A baby feels hunger: well,
  there is such a thing as food. A duckling wants to swim: well, there
  is such a thing as water. Men feel sexual desire: well, there is such
  a thing as sex. If I find in myself a desire which no experience in
  this world can satisfy, the most probable explanation is that I was
  made for another world. If none of my earthly pleasures satisfy it,
  that does not prove that the universe is a fraud. Probably earthly
  pleasures were never meant to satisfy it, but only to arouse it, to
  suggest the real thing. If that is so, I must take care, on the one
  hand, never to despise, or to be unthankful for, these earthly
  blessings, and on the other, never to mistake them for the something
  else of which they are only a kind of copy, or echo, or mirage. I must
  keep alive in myself the desire for my true country, which I shall not
  find till after death; I must never let it get snowed under or turned
  aside; I must make it the main object of life to press on to that
  country and to help others to do the same.”