The midwestern/general accent is branded as having no accent in America. It's the accent of choice for news anchors and radio hosts. Mispronunciation is more common in other dialects, and is more apt to take focus away from the subject.
Basically, in America you
are saying the words all wrong. It's funny. Sure, you could say that our accent is funny, but not nearly so much as your own. You don't have a defense