You'll get the following error in Raspberry Pi OS when locale is not properly set.
-bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8)
You can easily fix this via Raspberry Pi Software Configuration Tool (raspi-config).
Steps to fix setlocale error in Raspberry Pi (Raspberry Pi OS):
Run
raspi-config from the command line.
sudo raspi-config
Choose
Localisation Options from the main interface.

Choose
Change Locale from the menu.

De-select locales that you don't need (optional).
en_GB.UTF-8 UTF-8 is installed by default and could be removed.

Select
en_US.UTF-8 UTF-8 from the list and press
Ok.

Select
en_US.UTF-8 in the next screen

The selected locales will be generated, and you should no longer get the error.
Generating locales (this might take a while)...
en_US.UTF-8... done
Generation complete.
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