How to set LC_NUMERIC to English permanently?

Append the value to your ~/.bashrc file:

echo 'export LC_NUMERIC="en_US.UTF-8"' >>~/.bashrc

To make it applicable from the current session of bash, source the ~/.bashrc file:

source ~/.bashrc

Example: Here i am changing from en_US.UTF-8 to C:

$ locale | grep LC_NUMERIC
LC_NUMERIC="en_US.UTF-8"

$ echo 'export LC_NUMERIC="C"' >>~/.bashrc

$ source ~/.bashrc 

$ locale | grep LC_NUMERIC
LC_NUMERIC=C

This will change the locale for only the user running the command, for system wide change you need to add the value to /etc/default/locale, check the added portion below.

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You can also add the value to the systmwide locale file, /etc/default/locale, which will be read at start. To put it there:

echo 'LC_NUMERIC="en_US.UTF-8"' | sudo tee -a /etc/default/locale

Or

sudo bash -c 'echo "LC_NUMERIC=\"en_US.UTF-8\"" >>/etc/default/locale'