'Just the fact an inquiry is going ahead is a symbolic blow to Blair, and any finding that he doctored evidence to justify an unpopular war would be political dynamite, analysts said.

"In the U.S. people feel 'look, we've won, this tyrant has gone, why bother?"' Anderson said. "Here, there is a press hysteria over Tony Blair and WMD." '

Press hysteria, perhaps.
Inquiry = bad thing.
I would agree that it's possible that an inquiry, could be bad. Though generally it's thought a good thing (it you weren't completely clueless about the function of govt), that's Congress's job to review how various agencies are functioning. This is a normal event, alarm bells should ring if it wasn't happenning. Though maybe it's a bad thing in the UK.
It's also possible that Congress will turn the investigation into some witch-hunt, but since it's Republican Congress I doubt you get much more than grandstanding Waxman standing up and makling a fool of himself. Meanwhile the adults will do their jobs.