This is pure speculation!

But alright!

Let's assume that Britain woud have accepted that Germany invades Poland. Then it would have accepted that Germany would dominate the continent and that Germany would invade the USSR and fight Communism. This is not completly unlikely, Hitler always thought it would come this way.

Then there would have been no German / British war. Hitler never intended to attack Britain or the colonies. What about France? Probably France would not have dared to attack Germany. If Hitler was sure that France was no threat, he would have concentrated on the USSR. Maybe there would have been a change in the French government towards a pro-German, pro-European and maybe pro Fascistic government.

Hitler would have invaded Yugoslavia (perhaps) but not Greece. There would have been no German troops in Italy. There would have been no German subs in the Atlantic and no Allied blockade.

Hitler would have invaded the USSR. Maybe he would have won that war (although you should not underestimate the Soviets).

There would have been no cooperation between Germany and Japan. Britain, France and even the Netherlands would have been able to concentrate their fleets at the Pacific and there would have been no Japanese expansion.