What if the United States effectively ceases to be part of the Western world?

To answer your question, it could be the best thing since sliced bread, short of a global war.

The last sea-change in the world happened slightly more than 70 years ago at the end of WWII. Millions of lives lost and enough misery to go around forever.

From the ashes of WWII came the current world order. If we can rejuvenate this version without having WWIII it is a major win for everyone.

Remember, nothing is forever, and change is the only constant. You may not like the current cycle of change, but if history is any guide it will bring about something far better than we had before. Stop wailing and gnashing and get on with the change.