Apparently you are correct, but I wouldn't gloat over it...
Q: Did Sinclair Lewis say, "When Fascism comes to America, it will be wrapped in the flag and carrying a cross"?
A: This quote sounds like something Sinclair Lewis might have said or written, but we've never been able to find this exact quote. Here are passages from two novels Lewis wrote that are similar to the quote attributed to him.
From It Can't Happen Here:
"But he saw too that in America the struggle was befogged by the fact that the worst Fascists were they who disowned the word 'Fascism' and preached enslavement to Capitalism under the style of Constitutional and Traditional Native American Liberty."
From Gideon Planish:
"I just wish people wouldn't quote Lincoln or the Bible, or hang out the flag or the cross, to cover up something that belongs more to the bank-book and the three golden balls."
There was also a play called Strangers in the late 1970s which had a similar quote, but no one, including one of Lewis’s biographers, Richard Lingeman, has ever been able to locate the quote.
A useless post, not even worthy of the effort put forth.