Sorry but there isn't. I'm assuming that you didn't receive a denial e-mail. That e-mail usually has at the minimum some standard reasons why an application may be denied and often comments from the reviewer.
All I can think of is that the reviewer might have thought that this category was a bit big for a new editor. Besides the 75 listed sites there are a bunch of sites already waiting to be reviewed there. Sometimes that can be a bit overwhelming to a new editor. I suspect that this category may also be a bit of a spam magnet. There are some shady death care businesses out there who like to spam some categories. A spam magnet category would also not be a good choice for a new editor.
What about trying the U.K. or Canada category first? That would give you some experience before tackling the U.S. category.
Hope that helps a bit.