If Churchill did say this, it is sarcastic?

It is attributed to Churchill

NL888Did Chruchill mean to say "Don't count on the Americans, because they have tried everything except right things"?

No. He was saying that you can count on the Americans because they are very very persistent. Eventually they will get things right.

Churchill said: "You can count on the Americans to do the RIGHT thing after they have tried everything else."

Did Chruchill mean to say "Don't count on the Americans, because they have tried everything except right things"? No, he didn't mean that.
He meant that they will finall

CliveHe meant that they will finally do the right thing, after trying to avoid it.

That does sound more like Mr. Churchill. America stayed out of the war until it was attacked at Pearl harbor. Before that, they did help Britain, shipping them essential supplies, and escorting the fleets, protecting them from the submarines.
So I suppose that is what he

Well, it sounds that the right thing is the last that the Americans were willing to do."
Is the justice that comes too late still justice?

"too late?" Is that how you see it?

NL888 Well, it sounds that the right thing is the last that the Americans were willing to do." Is the justice that comes too late still justice?

It is meant to be a witty or clever remark, a kind of double-edged comment not particularly complimentary to the Americans.

You have to remember that he himself was half American, by his reckoning, and proud of it. He was speaking for the benefit of his fellow Britishers. And not even he could have such hubris as to imagine he had a corner on rightness. He was being mordantly witty, that's all.