Burgy61 - did they say why they were contacting you or how they got your contact details? Were they looking for reprint rights for a particular short story of yours (for example)? Were they looking to pay you for your contribution?
Appreciating that it's a new set up, the information provided on the site with regard to American Fiction left me a little confused. Specifically:
American Fiction is made up of the following sections; American Biography, Contemporary Writer, Selected Works. A writers directory and Horoscope. We Have two products for sale in American Fiction a writer's resource database and self publishing product. We also publish original selected works as printed media and audio books; there is a printed annual.
This makes it sound that American Fiction is both the title of an on-line magazine, but is also the name of a divicion offering specific POD and database products, without any further operation being offered as to how these might work, what the costs are etc. Unlike their publication, Modern Republic, there is no publishing date for when the magazine will be available and a quick Google search hasn't turned up an existing on-line magazine of that name (although I have found references to a print magazine of that title as existing in the 1940s).
Personally, I'd advise staying away from any organisation that sends you a generic email that doesn't contain specifics as to payment, what sort of material they're looking for etc. Duotrope is the first place I go to if I'm looking for markets for my short stories.
MM