other countries don't matter
but congress and public opinion do.
As you said a non-pre-emptive response to an attack that can be traced to another country, similar to the Afghanistan situation, will always be an option/possibility.
I believe it will be very difficult to get congressional and public support for A pre-emptive attack on another country for the foreseeable future. The evidence will need to be unquestionable and if it were that strong most of the western world would also sign on.
I do not believe there was deliberate deception on the WMD but there were obviously some intelligence failures that are at least a little bit embarrassing and the failures will be a topic of conversation for years, particularly when the subject of a pre-emptive strike is raised.