English pronoun cases don't divide up the same way Esperanto cases do (e.g., prepositions take the object case), but note that many English speakers say, "It is me" rather than "It is I". (I don't know Emile's first language.)

Right. I forget the technical terms used in the case of English (they aren't usually called nominative vs. accusative anymore), but the default case is 'me': 'I' is the special case, used only in subject position.

(The default case in English is actually descended from the Old English dative, not the accusative, with the exception of 'it' (OE nom. 'hit', acc. 'hit', dat. and gen. 'him' and 'his' just like the masculine pronoun) though the two merged for most of the pronouns in the OE period: it's only obvious from 'him' (OE nom. 'he', acc. 'hine', dat. 'him') and the pronoun 'they', which was borrowed from Old Norse (nom. 'þeir', acc. 'þá', dat. 'þeim').)