IIRC, there are no videos of 2008 US Nationals posted on YouTube because of the rights that IceNetwork.com has. I did find afew videos of 2008 Nationals on Youtube - I think I found Mirai's exhibition and I also found Belbin/Agosto FD. You might try icenetwork.com - I don't know if they still have Natioanls videos posted and if they do whether there is a fee to access them.
Mirai Nagasu fans have it hard on YouTube. All the performances she gave this year were either shown by IceNetwork and thus under their broadcasting rights, or not shown by anyone at all!
Though while I do know they're occasionally still making claims(one specific video I know they had removed within the past couple of weeks), I think the USFSA stopped being as aggressive about it as they have been. Possibly they realized it's not making them very popular with fans. Though I'm kind of hoping they eventually go through the system and have YouTube slap advertisements next to the videos so those of us with reduced bandwidth can see the performances and they can make more money.