The word empire is loaded but on the other hand not totally useless in describing the role of the USA especially since the end of WW2. There are other ways of describing it. For example -- dominant global hegemony.
In any case the "American empire" has overall been a positive stability promoting influence while it has lasted. Of course far from perfect but much better than any other available alternative.
As far as it's decline, that was already in a slower phase of happening already before the ascension of American autocrat Trump who rejects the role of leader of the free world.
What Trump is doing is to GREATLY ACCELERATE that decline.
What I consider enemy states such as Iran, North Korea, and Russia, etc. are celebrating that gift that the maga fascist cult has given them.
Decent Americans and traditional decent American allies realize that such rapid acceleration was unnecessary and is VERY DANGEOUS.
Now for better or worse (worse) everyone in the world is going to have to adjust to this radically different new reality.
Especially Americans.