Yes. The claim was comprehensively debunked by Radio 4's More Or Less.
"Testimony to the US Congressional EMP Commission" did not state that claim. One of the committee members had read this 90% number in an entirely fictional sci-fi novel. He asked the testifying expert whether it was plausible. The expert gave a fairly non-committal answer that could be construed as an affirmative. Bingo, every two-bit newsertainment organ starts repeating the claim that an EMP would kill 90% of Americans.
Biting the hand that feeds IT
