I just migrated to worpress and want to remove all of the 'uncategorized' categories, since all of my posts are now all categorized. Is there a way to do this easily?
Yes, you can. By following what @Innate said, I created a new category called "General". All the bulk posts I created earlier (from BulkPress plugin) had "Uncategorized" and "my-own-category" (added by Bulk edit). Then, I chose "General" as my default category under Settings > Writing. Next, I deleted the category "Uncategorized". "Uncategorized" was removed from all the posts, leaving "my-own-category" as the only category. Plus, all new posts that I don't create a category for will be marked as "General", which I like more than "Uncategorized".