>why not pledge to the country USA or love or the president<
I don't know where you were educated, staytrue, but the AMERICAN flag represents the country USA, and the allegiance IS to the USA. As a matter of fact, I'm going right out to display my AMERICAN flag.
Here is the deal. Ask a student that if you add 4 oranges and 3 apples to 6 oranges and 7 apples and they will give you the correct answer. Ask a student what 4x + 3y plus 6x + 7y equals, and their brain locks up.
a pledge to the USA, they would get and proudly say, a pledge to the flag, and they are just mouthing the words.