The post here should help you understand why you cannot delete components: https://groups.google.com/forum/#!category-topic/mitappinventortest/k48uyPMyaRw
The post explains what you probably did. You need to reset the Chrome settings so it can allow the Chrome browser to delete components while using App Inventor ..the post explains how.
Simplified: the cure, with Chrome is to type chrome://settings/
in the browser's URL box and get this screen
and press reset settings.
Did the advice help Joseph?
Regards and Merry Christmas,