persisting locale

Question

I want my web browser, terminal emulator, and nautilus to show in English, and I tried to set english system-wide in language support, but it didn't change except the date on the top and the gray password in login manager. How can I fix this? And what is the cause of this? Mine is 20.04 LTS.

$ cat /etc/default/locale
#  File generated by update-locale
LANG=en_US.UTF-8
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"

$ locale
LANG=ja_JP.UTF-8
LANGUAGE=
LC_CTYPE="ja_JP.UTF-8"
LC_NUMERIC=en_US.UTF-8
LC_TIME=en_US.UTF-8
LC_COLLATE="ja_JP.UTF-8"
LC_MONETARY=en_US.UTF-8
LC_MESSAGES="ja_JP.UTF-8"
LC_PAPER=en_US.UTF-8
LC_NAME=en_US.UTF-8
LC_ADDRESS=en_US.UTF-8
LC_TELEPHONE=en_US.UTF-8
LC_MEASUREMENT=en_US.UTF-8
LC_IDENTIFICATION=en_US.UTF-8
LC_ALL=

$ echo $LANG
ja_JP.UTF-8