Were the British Empire to fall the Powers would stampede for the spoils, Germany inclusive.
Germany is incapable of doing so. Africa and the Middle East? Requires Italian assistance and would thus wind-up going to Italy? British Asian Colonies? The Germans are incapable of reaching those and thus they would go to Japan. The America's? The United States would react
harshly to any Nazi attempts to interject.
Germany is simply incapable of acquiring British colonies before other powers. That only leaves the Soviet Union.
That's an argument for Sealion.
If one ignores that it would fail. You've expressed the delusionalism on other threads that it would not, but since you've never managed to prove how it would while others have provided plentiful proof of how it would not. I mean, sure Hitler would go for it if he thinks it could provide him the quick victory. But it won't. And with it's failure, in his own mind and the mind of his generals, the only other option to avoid a prolonged war which Germany cannot win is to invade the Soviet Union before it gets too powerful.
That this would still lead to a prolonged war which Germany could not win was a result of Hitler not understanding what the USSR had already managed to achieve.
The Barbarossa argument was whether eliminating the SU could leave Germany in position to defeat the Anglo-Americans.
And with the failure of Sea Lion, that argument gains extra-strength.
We know now that the USAAF would rip Germany to shreds in 1945/46 in either case, but at the time what Hitler was doing was balancing the risks between the options.
And he perceived fighting the Soviets in 1941 to be the lesser risk. With the failure of Sea Lion, that perception would be confirmed.
Hitler perceived no 'window' for attacking the SU based on Russian strength.
Yes, he did. Repeatedly during Barbarossa he justified his strike as a pre-emptive (although in reality, the correct term would have been preventive) strike against the Soviet Union before it became too strong. Most explicitly at one meeting, he showed his staff intelligence reports of the Soviets construction of new armaments factories in the Urals and explicitly declared:
"Now you see how far these people have already got. We must strike at once!"
Hitler was very much aware that when it came to waging the war needed to achieve his goals, time was not on his side. So he had to strike and strike fast.
The US wasn't even in the War in June 1941 or when planning for Barbarossa begun so that assertion to defeat the anglo Americans is wrong
It's not entirely wrong, it just isn't the whole story either. Hitler had a variety of reasons for Barbarossa among them the possibility that victory in Russia would bring Britain to seek terms and the acquisition of resources in case they didn't and the US did enter the war (because US involvement was clearly growing, what with the neutrality patrols and lend-lease). The strategy doesn't stand up to objective scrutiny, but the German military system never really subjected it to that and the few individuals who did and voiced their concerns were duly ignored. So waging war against the USSR as a means of putting Germany in a better position to fight the Anglo-Americans was indeed one reason. But so were others: Nazi ideologies demand for lebensraum, forestalling the growth of Soviet military power, Nazi racism, the Germans problematic economic situation, and many more were all factors that combined with the general strategic situation to push along the decision to invade the Soviet Union, as well as the equally important decisions of "when" and "how".
Although, put it bluntly, viewing Germany's strategic situation in WW2 objsective it is clear they are between a rock and a hard place: a quick and speedy invasion of the Britain is guaranteed to fail. A quick and speedy invasion of Russia is also guaranteed to fail. To wage a naval-air war against Britain plays to Germany's weaknesses (the lack of a proper navy and strategic air power), accelerates American entry into the war, which then makes trying to wage a naval-air war against Britain an exercise in futility. To try and knock the British out through the Mediterranean Strategy runs into problems of logistics, the lack of naval-air power, and over reliance on inadequate allies. And ignoring Britain isn't in the cards because Britain isn't going to let themselves be ignored, what with the air raids, blockade, and peripheral campaigns. Trying to rope Stalin into the Axis Pact just means turning Germany into a Soviet client state while Stalin sits around and does nothing but get stronger.
Any strategic option they go for is going to suck. But given their ideological blinders, the Germans thought they were picking one that would succeed.