I Had my Teeth Whitened with Bleaching Gel from my Dentist, Above the Crown my Gum Has Gone Black Can This Be Corrected Easily?

Whitening gel is very effective on enamel and dentin, but not that effective on the cement that covers the root. If the tooth had previously root-canal treatment it can lead to a darkened root. Most likely whitening improved the overall condition, but still for more aesthetic results you can get soft tissue surgery to cover recessed gum and a full crown.

I doubt very much that the gum got darker due to the bleach. If anything, it would temporarily get bleached a whiter color. I have a feeling you are just paying more attention to your whiter teeth and are getting more critical of pre-existing conditions. It is very common for the gum around an older metal-based crown to darken. The crown can be replaced with an all porcelain crown.