Am I to understand from some of the "Experts" on here that I can Fly Night & IMC in USA now? when I have been told & heard that they are NOT Valid in USA???
Ignore the "experts". IMC rating is only ever valid in the UK.
You may fly at night in the US on a 61.75 provided your JAR licence has the words "the privileges of this licence may be exercised at night" written in it. Which it will do if you have done the UK night qualification.
You may have been told the night rating is "not valid" in the US because in the US there is no concept of a night rating...basic PPL includes it.