There's nothing from the US yet, as I suspect (not that I am privvy to an inside track on RIAT these days) that negotiations are still ongoing.
Last year's US participation was pretty impressive (from memory - B2, C5, KC10, E6, plus the head honcho in his Gulfstream and others I have probably forgotten) so I can't think it would go from that to zero in a year.
I do agree that the overall list might look at bit lacklustre (though the Breitling Super Connie will do it for many) but also have a feeling there might be at least one big announcement still to come....the clue is in the artwork on the
Royal International Air Tattoo homepage.