That is a silly question.
Had germany focused on destroying britian (and they were doing a good job of it) it would have completely removed the british from the equation. The germans were doing a good job, but they had started splitting their troops in 1940 s they could attack the russians. The german wolfpacks (uboats were demolishing all the shipping into britian) and the battle of britian was ongoing. The germans could have forced the british to surrender and then focused on russia.
The germans could then have focused solely on the Russians. If they had waited to invade, the US would have had no where to stage their troops for european fighting. The germans would have defeated britian and then could have went after the soviets when they were fighting vs the japanese.
Of course the germans could still have won if they hadn't been so all over the place when they were attacking the russians. they sent troops to places they shouldn't ahve, they fought in places that favored teh defenders...