Since World War II it is difficult to recall a time when the United States faced as many pressing issues and crises.
It is difficult to think of a time since World War II when the United States had to deal with as some difficult problems and crises as it does now. It is difficult to think of a time since World War II when the United States has faced since several difficult problems and crises.
Since World War II it is difficult to recall a time when the United States faced as many pressing issues and crises.