The Uk flag is in the footer.
As you are in the US you should select en_us in pwsWD/_my_settings/languages.txt
# $scrpt_vrsn_dt = 'languages.txt|01|2020-12-16'; # release 2012_lts
#
# key | flag |locale |language file |description setup/menu |countryFlag|wu locale |
#en-uk |uk.svg |en-gb |lang_en.txt |English (United Kingdom)| |en-GB|
#en-au |aus.svg |en-au |lang_en.txt |English (Australia) | |en-GB|
#en-ca |us.svg |en-ca |lang_en.txt |English (Canada) |can.svg |en-US|
#en-ie |ire.svg |en-ie |lang_en.txt |English (Ireland) | |en-GB|
#en-nz |nz.svg |en-nz |lang_en.txt |English (New Zealand) | |en-GB|
en-us |us.svg |en |lang_en.txt |English (United States)| |en-US|
All lines with an # at the first position are skipped
All other lines are used.
Wim
