Learn French: J'espérais l'annulation de cette réunion. - I was hoping for the cancellation of this meeting.

This is called the imparfait d'atténuation (softening imperfect). Just like in English when we say "I was hoping" instead of "I hope," using the imperfect makes the statement sound less direct, more polite, or less demanding. It is very common in professional or delicate situations.

Could this sentence also just mean a literal past action?

Yes! Without context, J'espérais can either be the polite present ("I was hoping we could cancel...") or a standard past action ("Yesterday, I was hoping for a cancellation, but it didn't happen"). The surrounding conversation will make it clear which one is meant.

Is réunion a false friend? How do I say "a family reunion" in French?

Yes, it is a partial false friend! In French, une réunion almost always refers to a business or organizational "meeting". If you want to talk about a "reunion" in the English sense (like gathering with family or old friends after a long time), you would use the noun des retrouvailles.

Notice the accent on espérais. Doesn't the verb espérer change its accent in some tenses?

Exactly, it is a stem-changing verb. In the present tense, the accent flips to an accent grave: j'espère. However, the imperfect tense is built from the nous form of the present (nous espérons), which keeps the original accent aigu. Therefore, all imperfect forms of this verb keep the é, as in j'espérais.