Well this will be Great for everyone, but Russia and possibly Japan.

Italy makes a killing selling supplies to Hitler and Japan, which may even keep Japan from attacking depending on whether Mussolini's Ship building plan stays on task and doesn't bog down in red tape and graft. Even if it delays the Pacific War Six Months, that a big difference in American Fighting Power.

How I see it. 1940 Mussolini doesn't invade Greece and get his Army defeated and humiliated. This in turn doesn't cause the Yugoslavia coup. Hitler in turn doesn't have to clean up Mussolini's Mess which in turn doesn't result in his Ju-52 force being trashed (the Airborne suffered more causalities in Holland than in Crete), this eases Logistics in Barbarossa. Two Panzer Divisions are not trashed in the Mountainous terrain along with half of Army Group South's Fuel reserves, so they can kick off their offensive on time.

Earlier start to Barbarossa in Late May/Early June with Paratroopers landing behind Soviet Lines to secure Bridges and Ambush Soviet Supply Convoys along with other Mischief will enable even more Super Cannaes especially in the South, though its an open question whether the Wehrmacht takes Moscow or not though.

Oversea Trade for Italy. Churchill can not afford to piss off Mussolini. Thats not to say Pirates can't deal with his Merchant Marine There are many Pirates and sadly the RN can't catch them all...

UK becomes irrelevant without the U.S. in and Hitler doesn't get the feeling of the U.S. being against him, so he isn't going to declare war on them.

For the U.S. that means they don't lose over 400 ships to German Subs which means they can ramp up production faster and get that production to the Pacific Faster...

Thats all the time I have signing out.