Why is it called the Good Ole US of A -- The US is not really that old compared to most of the other countries on this planet?

Answer 1

The 'old' in 'Good Ole ....' (i.e. good old) is not referring to age, duration, or any length of time.
It just means something that has become familiar to us and that we can rely upon e.g. to do something, or to follow a particular pattern.
'Good old ...' is a term of affection, for someone or something.

e.g. Good old Joe. He turns up at 6 o'clock every morning, rain or shine!

It can also be used in a slightly sarcastic, but still affectionate, way.
For example, this expression is used when describing someone we are fond of, but who can always be relied upon to do something wrong, or to someone who frequently but inadvertently always seems to get themselves into trouble!

e.g. Good old Bart Simpson!