Answer:
A job that involves sitting in a highchair, wearing a black gown and smacking things with a mallet
Every country has one, though we are not the same. Waving to our citizens, throughout the wind and rain. What is it?
I'm a starchy plant tuber that is one of the most important food crops, cooked and eaten fried, such as french fries.
A standard dimension for sandwiches and rulers
What is used by man, tossed by trees, everywhere but unseen?
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.