Britain is a currently a shadow of its former self, if the Empire that it once was. However, when she decolonised, did the Empire have plans in place to continue maintaining her power// following a policy of imperial ?
I think your question is misplaced, what era did America force Britain into decolonisation?
It can't have been the American revolution, as the empire only grew after 1783, and didn't peak until 1922 150 years after the American revolution.
If you are speaking of post WWII, then it was Britain herself who forced herself into decolonisation. India the jewel in the crown gained independence in 1947, and since Britain had to rebuild her own economy, decolonisation soon followed.
It wasn't America who forced Britain to decolonise, it was two world wars.