I believe your question is somehow related to ‘subjunctive mood’ in English, and I would like to touch base on this topic. One of the functions of subjunctive mood is to express an idea or a statement that is contrary or hypothetical to real present. In such cases, the past form of ‘to be’ verb (is/am/was/were...etc) is always ‘were’, regardless of the subject, gender, and number.
(1) If I were a bird, I would fly around the world. (But, I am not a bird now)
(2) If it were a bird, it would fly around the world. (But, it is not a bird now)
(3) If he were here, he would invite you. (But, he is not here, now)
(4) If I were a political leader, I would always think about public welfare. (However, I am not a political leader, now)
In all above cases, regardless of the subject and its gender and number, the past form of ‘to be’ verb is always ‘were’.