Maerion
I agree that some American celebratory customs are now becoming commonplace in the UK but promenading is nothing new c/f our Proms music series and its origins. Prom night in colleges seems to have originated at Princeton in the early 1900s; Baby showers were given by American church ladies, again in the early 1900s. These customs have taken a long time to get here.
Language is another matter. I think cookies and biscuits has been discussed before with cookies very much a Scots term that was taken to America.
Knickers is interesting as it originates in America via a novelist and a Dutch colonist.
Knickers is a colloquial contraction of knickerbocker(s) - a loose fitting garment gathered at the knee. Knickers is now used in the US for the shorts worn by boxers and footballers. The Liverpudlian kecks for trousers derives from knickers or knickerbockers.
Harmen Jansen Knickerbocker was a Dutch colonist most associated with Albany, New York.
American writer Washington Irving (1783-1859) used the surname to create the fictitious Diedrich Knickerbocker, the pretend author of Irving’s novel A History of New-York from the Beginning of the World to the End of the Dutch Dynasty published in 1809. The character dresses in baggy-kneed trousers referred to as knickerbockers, later shortened to knickers.
en.wikipedia.org/wiki/Diedrich_Knickerbocker
Knickerbocker is also used to refer to people who live in Manhattan and the short-form adopted for the city’s professional basketball team who are called the Knicks (and wear knickers to play in).
In 1900, The Times reported The Imperial Yeomanry.. in their well-made, loosely-fitting khaki tunics and riding knickers.
The earliest written British use of knickers for womens’ undergarments was in 1882. I recommend flannel knickers in preference to a flannel petticoat. (From The Queen - an illustrated journal that was published from 1861 to 1970.)
Pants comes from mid 14C to early 17C Middle French panatalon - also the Italian dramatic character Pantaloon (pantaleon) who worn long, straight close-fitting breeches.
Pants became trousers of any kind. In early use, the word was applied to men's trousers, but in the 20C extended to include those worn by both men and women. Panties were men's or boys’ short trousers.
Panties for women's or girls' underpants; especially short-legged pants with an elasticated waist - is a relatively modern term first used in the early 1900s in Australia.
In summary: Pants is French. Panties comes via Australia. Knickers comes to us from American fiction via a Dutch colonist. It’s all very international but if you insist on knickers as the correct term you were already using a word that originated in America.
If you live in NW England ( as I do).....all trousers are called pants


. Perhaps we can set up a “Ban the Bad use of words” group ? … oh heck that’s a terrible use of grammar, I blame my ageing brain.