Germany certainly had an advantage against Britain alone.
The colonies certainly where behind Britain in a major way... New Zealand had over 50% GDP on the war effort and about 10% of the population served in the forces.
If it was Germany vs British Empire (Japan staying in China) then it would have been hard on the British as it was more spread out. However without having to fight the Japanese it would have allowed the massive British Navy to concentrate in the long term on the Germans. Also more colonial forces could have been devoted to the North African campaign with no Japanese threat.
The issue is though if Germany was solely against the British and concentrated its forces on military targets it could have isolated the British islands and destroyed any effective air cover. This would have then meant all the navy would have to defend against airplanes around Britain. So the British would have lost their airbases then their ports and then their fleet that remained behind. This would have made it relatively easy for the Germans to mount an invasion, all it would take would be the fleet to carry the men across... maybe massive support by paratroopers.
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