[ZenGum]

Riddil, I disagree with your account of the demise of Europe.
During the 1800s, they were not complacent and resting on their laurels. They were competing frantically with each other to dominate the continent and the world, innovating and competing as much as they could. In 100 years they seized most of Africa, South and South-East Asia, and kept shoving amongst themselves.
I believe there were two main factors in the demise of Europe. Firstly the colonies caught up the technological and organizational advantage that Europe had held. Secondly, the two world wars exhausted them. In 1914, the USA was worthy but not as powerful as Britain, or even France or Germany. By 1946 the USA was clearly the strongest. I think that pouring their national resources into destructive wars was the crucial factor in the demise of Europe.