It seems clear that Britain lost a substantial amount of men (manpower) and wealth as a result of the two world wars. 900,000 men in WWI, 400,000 in WWII (compare to about 400,000 Americans but the US had a population 3 times the size).
I’ve heard figures in the past about how much wealth Britain lost in WWII. I don’t recall, but it may have been as much as a third of the entire net worth of Britain was lost in WWII, mostly to the US.
Boatloads of gold sent over the Atlantic to purchase tanks/equipment food fuel etc. Britain mortgaged her future in order to survive. A good trade I would say.
But other countries lost even more men and wealth, yet seemed to bounce back more quickly.
The UK suffered as a result of leftist goverments and policies; but geopolitics are complex. I think the decline of the British Empite started before WWI, and many factors sped the decline. The two wars were certainly two of the more significant.
If the wars had not happened, I do not think Britian would be more powerful then the US today. The US was poised to become a great power, wars or not. The wars sped US growth, as they did the British decline.
Although Britain is not the superpower it used to be, it remains one of the seven wealthiest countries in the world, and is one of about 8 or 9 nations (out of 200) with nuclear weapons.
My grandfather told me how his school books marked British lands in red. The red was around the globe. The largest empire the world has seen.
However, the sun has now set on the British Empire.