This is one of those AH moments that comes slamming up against our bedrock preconceptions. We- especially the Americans on the board- have spent the last couple of generations building up this idea of the impossibility of an early or "easy" peace with Japan. It permeates so many aspects of our culture. (As an aside I just finished Shogun and it's amazing how much of this book about 17th century Japan reads as a justification for the A bomb.)
Pulling back the decades and trying to imagine how people in 1942 would feel about it...so tough! And I think that's something we should look into; not just what the men in tops and tails think is fair, but what they have to sell to their countries.
I think other posters have laid out the non-US viewpoints pretty well. To sum up: "Fine, yes, whatever, could you just GET YER ASSES TO EUROPE PLS? (But seriously, I want my shit back.)"
But the American viewpoint? Much more complicated.
You had this fire in the nation's belly over what was absolutely considered to be the most despicable and cowardly act of all time. We can debate here whether or not Pearl Harbor was really all that perfidious, but that was the drug in the national bloodstream at the time. That's a point against a reasonable treaty as a political reality in the US.
I also find myself thinking of the lengths the government went to to shift the public's loathing to Germany. The needs of Europe-First required it, and it seems to have mostly worked. By 1942 Hitler's the Big Bad (I mean it doesn't really take that much effort when it's Nazis, I guess, but still, it was an accomplishment). And in 1942 people are still being sold on Germany as a nigh invincible enemy. The fact that the US swamped the world with war material and (ultimately unused) divisions, ships, and planes points to the fact that most everyone at every level bought into the idea of Germany as an invincible enemy to some extent. So if that's what's driving people by 1942, you might be able to convince them that a non-retaliatory peace is necessary.
I just wonder if people might follow this train of thought: the need to prosecute the war in Europe is ultimately serving our need for retribution over the attack on Pearl Harbor, even if prosecuting the war in Europe is our most immediate goal. We're removing the ability to get retribution for Pearl Harbor in order to better prosecute the war in Europe. Does this counteract the propaganda machine sufficiently to cause trouble for the Roosevelt administration if they go forward with a treaty?
I guess it all hinges on how much people have been converted to the cause of the European war by 1942 to the sublimation of the Pacific war. And possibly how much the US politicos feel they can get away with in terms of the exigencies of war.