It is good, it is bad, it is powerful

1. Take 0 out then you are really in it

2. Take 1 out then it is unreal

3. Take 2 out, then you are back to 1

4. Take 3 out, then you are now in US

5. Take 4 out, then you are back to 0

What word am I?

Hint 1

The numbering of the clues is part of the puzzle.

Hint 2

Numbers are part of the word

Hint 3

Starts with a vowel and ends with a vowel

Hint 4

Five letter word with 3 vowels

This layered word may be

ozone

1. Take 0 out then you are really in it

(o)zone - in the zone

1. Take 1 out then it is unreal

oz(one) - the magical Land of Oz

1. Take 2 out, then you are back to 1

(oz)one - giving one

1. Take 3 out, then you are now in US

(ozo)ne - removing three letters gives Nebraska

1. Take 4 out, then you are back to 0

o(zone) - removing four letters leaves o for 0

Title: It is good, it is bad, it is powerful

good - its layer absorbs the Sun's harmful ultraviolet light
powerful - it is a very powerful oxidizing agent

I think the answer might be

Span

1. Take 0 out then you are really in it

The span of something is its full extent, end to end which we could claim to be in.

1. Take 1 out then it is unreal

Take one letter out and we get Pan, which can refer either to the Greek God or perhaps Peter Pan

1. Take 2 out, then you are back to 1

Take two letters out and we get an - the form of the indefinite article used before words beginning with a vowel sound, indicating one.

1. Take 3 out, then you are back to 1

Take three letters out and we get a - the form of the indefinite article used before words beginning with a consonant sound, also indicating one.

1. Take 4 out, then you are back to 0

If we take all four letters, there are none left.