Yeah, they think it's a typical GM clown response. Does GM think the cars aren't going to end up on a racetrack together in the US? Uh, no. Does GM think they can beat GT500 in 0-60, quarter mile, high speed, all of which are way more realistic for 99% of owners? Uh, no. Does GM honestly believe Ford will take the bait on an empty challenge to waste a bunch of time and money sending cars and staff to Germany so GM can maybe hopefully eek out a miniscule victory at a race track 99.9999% of their customers will never see? Uh, no. There's a reason they didn't issue a challenge at a specific track both cars have already been at here, and I'm sure it's because they've already been told they are slower. But hey, hang on to hope, even if the reality is your customers almost unanimously prefer drag racing to road racing.
GM would get a lot less grief if they didn't act like butt hurt little girls, but that's what they do best. I mean seriously, who writes a letter to their customers saying their competition should thank them for inspiring them to beat their ass so bad?