Was the war part of the reason that many European powers began to relinquish their colonial possessions?
It broke the bank. The UK, France, etc could not afford to maintain the colonies.
The UK had to sell off bases to the US for material and was massively indebted to the US in general. In fact only a few years ago did the UK finally pay of its final loan. Though it took that long due only to the favorable interest rate the US gave to the UK.