And do not expect to hear back from them quickly after you submit. I submitted a portfolio over a month ago and have not heard anything back even though they said they would contact me shortly after receiving my portfolio.
Probably depends on their need in your area. I know the guy that does the new photographers also shoots and he's an editor so it takes him a while sometimes. I sent them a bunch of magazine tear sheets when i filled out my stuff for them and heard back in 2 days (almost 2 yrs ago now). I think when they went off the spec format they filled most of their needs
Jeremy has it right, I believe. If you're in a town/area where USATSI already has plenty of photographers, you're probably not going to hear from them for a while, if ever. However, if you're somewhere there is a need, you'll find they're more responsive. In a perfect world, all emails would be answered, but how many of us believe the world we live in is perfect?
Also, in larger areas, where there are many photographers working as stringers for several agencies, when there is a new opening (somebody moves out of the area; gets too busy with other things; gets out of photography; etc.), it's very possible that USATSI will attempt to fill that void with a photographer who is already known, from the local roster of qualified shooters.
Go on the USATSI web site and do a search for your town or region. Take note of how many photographers there are, and how often each of them seems to be shooting. As a reference, in my kinda town, USATSI has three primary photographers, one or two folks who are used to fill in the holes (who also shoot for other wires), and the aforementioned Director of Photography who also occasionally shoots. This is a big media city: we have 2 MLB teams, an NHL team, an NBA squad, an NFL team, an MLS franchise, one from the WNBA and 2 Div 1 NCAA schools - and we cover pretty much all events with only 3 photographers.
Jeremy and Denis has it right. Figure when I applied I was told it would be tough to get anything from them due to all the photographers they had in the area.
All that I've read here makes perfect sense to me.
I will add that if the J. Brevard guy offers you any advice off of the message board be sure and pay heed. He absolutely and positively launched my sports photography career for me a few years ago with a quick message, and for that I still put up with him