The sentence is awkward, to say the least. "It wasn't me" - - why not, "It wasn't I". We would normally say, "I wasn't it", rather nan "Me wasn' it". Please excuse my punctuation. It's a reason why I need this site.
Instinct tells me that a more correct form of the sentence would be, "It wasn't me; I didn't break it."
I'm not sure why, from a technical standpoint though. The example just sounds wrong.
People who say 'I never broke it' do not say 'It wasn't I'.
Dalraita-- it perhaps "just sounds wrong" because "never" implies that it may have been broken more than once. For example, "I never broke a bone" as opposed to "I didn't break a bone". It's not grammaticaly incorrect, it's just giving more force that is perhaps necessary: "I didn't break it" would do. "It wasn't me" is perfectly acceptable colloquial UK English; in fact "It wasn't I" is definitely incorrect, since the first person is the subject ("It" being the object), thus "me"-- "It" being an elision of "The person who broke the thing".
In the past, it was considered proper English to use the nominative form for predicates, e.g "it is she", or in this case "It wasn't I".
In reality, this rule is used infrequently now, and I think we have a new unspoken rule: that the 'subject pronoun' is only ever used in the subject position.
So, instead of "I am the man. The man is I", we say "I am the man. The man is me".
I think it's time to let the old rule go.
'Me' is used improperly here, Though it's how people use it and it's widely acceptable, 'be' is not a verb of action then it doesn't call for an object pronoun after. 'This is I', 'It's I', 'It wasn't I', 'I'm not he', 'It seems to be she', etc, are all proper use of pronouns after linking verbs. Object pronouns normally come after verbs of action.
It and the pronoun are referring to the same person. "me" is not the object of the verb be. Therefore me is grammatically incorrect. But that doesn't mean that idiomatically it is being used incorrectly.