There can't and won't be a full-strength american millitary operation. There simply isn't a nation to target. For all it's super-power stance, the US can't simply run over a nation for a few terrorist groups inside it.
What I do
think will happen is two-fold:
1) The US will be forced to take pinpoint actions against the perpretrators of the attacks (most likely Bin Laden's group, thought you're right, Stryke - we still can't be 100% sure yet...)
2) The world will come down on Israel's policy of targeted terrorist assinations much less than before.
EDIT: About the Afganistan attacks, here the assumption is that it's not an "official" american response, but more likely someone taking advantage of the situation. Could easily be wrong, though. We'll just have to wait and see.
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[This message has been edited by sandwich (edited 09-11-2001).]