Subject-verb agreement

[toedrika]

Dear Professor,

There is no subject-verb agreement in these sentences:

"It’s (singular) bad manners (plural) to talk with your mouth full." - (from Longman dictionary)

"İmagine there's (singular) no countries" (plural) - (from the song İmagine by The Beatles)

Thanks and kind regards
Antoine Ghannoum

[Alan]

Your assertion is half-correct.

There is subject-verb agreement in the first sentence (subject: it, verb: is), but not in the second.