Well, there is no evidence presented that clearly puts them at the helm of 9/11. But even if so, the nation of Afghanistan is not related to Al Quaeda. In fact if you want to allow for this kind of sloppy logic, we need to start bombing Canada, England, Germany and The U.S. because all allowed Al Quaeda to operate within their borders.
The nation of China clearly brought down one of our planes. If we weren't bullies, then we could have easily attacked China justifiably. Why didn't we? Because we don't like the odds.