If I didn't ask this question, it would make no difference to my academic results.

[5jj]

I know IF I WAS.... can be regarded as non-standard English (or colloquial)if it is a counterfactual conditional sentence,

'Was' is natural English for many native speakers of British English today. There are still some who regard it as sub-standard.

but how about when the subject is not I, but a city, a car, etc.?

For example, a sentence: if the country was destroyed by a monster, we would all flee.

Would it be considered colloquial and be better if I changed WAS to WERE?

Even some of the people who use 'were' with 'I' use 'was' with other subjects. It is always correct to use 'were' in such cases, though it may sound stilted to some speakers.

[philo2009]

Thank you philo2009.

I remember last time when we were talking about a conditional sentence your answer could even refute a native speaker's answer.

May I have your opinion on my original question?(the title of the thread)

(if there's any part unclear in my original question, please let me know and explain the context)

It's a little strange. I imagine that what you meant was

Even if I didn't ask this question, it would make no difference to my academic results.

There is nothing grammatically wrong with this, but, as written, it implies that you regularly ask this question (and perhaps you do).

If, however, you intend specifically to refer to a question asked on a single occasion in the past, then, naturally a mixed third conditional

Even if I hadn't asked this question, it would make no difference to my academic results.

would be the appropriate choice if the academic results were still pending, or, alternatively, a paradigmatic third conditional

Even if I hadn't asked this question, it would have made no difference to my academic results.

if the results were already known at the time of utterance.

The choice is yours!