"Whilst", "while", and British and US English

Some of my students write "whilst" where I would use "while". I thought this was a distinction between British English and US English, so I checked some linguistic corpora to see if that is true. The British National Corpus of 100 million words created through 1993 has 5695 uses of "whilst" and 54,067 uses of "while". The Corpus  of Contemporary American English, which is more recent (1990-2019) and has one billion words, has 4817 uses of "whilst" and 662,619 uses of "while". So "whilst" is not the preferred term in British English, but it is ten times more common (or it used to be) in the UK than in the US.  (Andrew Shields, #111words, 29 October 2022)