I've been musing on the evident differences in similar cultures.

For instance, above Ms Cornish said- and it was accepted by other UKers - that it was common in 'the old days' for girls' bottoms to be pinched, implying no one thought anything of it.

In the US, unless I am greatly mistaken, bottom pinching of young girls would always have been considered beyond the pale. Cheek pinching (of the facial variety), yes. But bottoms? No.