Answer:
Every country has one, though we are not the same. Waving to our citizens, throughout the wind and rain. What is it?
When is 1500 plus 20 and 1600 minus 40 the same thing?
I am someone you don't know. Who am i?
Barren location, infertile and dry; my name means "to leave", it's not heard to see why
Humans have two that shrink in the light and expand in the dark
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.