Here is the reason why the provision inserted into the patriot act, that U. S. Attorneys can be replaced, without Congressional oversight, is likely to be unconstitutional.
If you are wondering why I feel this is an important issue here is my brief explanation. U. S. Attorneys are often the first line of prosecution in Federal corruption cases. If you are a corrupt administration you could simply replace U.S. Attorneys that are investigating the corruption with U.S. Attorneys that are friendly to your administration. Remember, the Administration gets to appoint U.S. Attorneys at the beginning of their term. As it stands, they must be approved by Congress. Here is the rub. If you ask an attorney to step down, the replacement does not need to be approved by Congress under the new Patriot Act.
If you don't believe that any Administration would go so far as to fire a U. S. Attorney working on a case the Administration found embarrassing, then you should look at the cases that the current group of ousted U.S Attorney's was working on, and then look at the political backgrounds of who these attorneys are being replaced with. Here is more information.