Isnt hindsight a wonderful thing?To go even further,if the UK did not side with Russia in WW2 and instead sided with Germany as Hitler wanted,Communism never would have spread beyond Russia's borders,Europe would be 100% European,all of Asia would be as prosperous as Japan,the whole Islamic world would have remained under the rule of princes rather than nutjobs,North Korea and China would not be threats to anyone.
Downsides?The US would not have had the chance to enter WW2 and therefore not claimed the spoils that made it a superpower,Israel would never have existed,France would not exist,and although Europe would be 100% 'European',it would be so in the 'Aryan' sense,ie,100% Anglo,Nordic and Germanic.The whole slavic race from Poland to Russia to Yugoslavia would have been easily wiped out by a combined British and German army and resettled by Aryans as was Hitlers plan.
Downside: Poland empty of poles since it Lebenroumen. Russia enslaved. Jews exterminate. Germans become Islamic anyway since Hitler wrote many letter where he believed to Islam as religion of choice since Christianity very weak.
Asia under Japanese Iron rule and many peoples exterminated (maybe you forget slaughters of Chinese?).
If not for damned Germans, Bolshavik not power in first place...since damned Kaiser give then 50 million gold mark. Oh and National Socialism was Bolshavism light...some improvment. Don't salvate too much.