Hello h2omedia,
You can uninstall JA Multilingual component normally as you do with other extensions (navigate to Extension Manager page and select extensions to uninstall)
To get your site work back as single language site, you need to follow below steps:
– On Language Manager page >> select Content tab >> disable all language except the default one.
– On module manager page >> search and disable all instance of “Language Switcher” module
– On Plugin manager page >> search and disable “Language filter” plugin
– You might need disable categories and articles of languages that you disabled.