Not really... there were many people of many nationalities that were killed or are missing in the world trade center. Watch TV. Japanese, Germans, British, you name it. More than just Americans.
Despite how many nationalities were actually in the building, the World Trade Center is a (the?) symbol of US capitalism, and it was definately a blow against America as opposed to capitalism in general.
The thing that really gets me is what if they had crashed into the White House, like they were allegedly planning to do? I don't know if it's really the truth if they were planning it, but could you imagine America without the White House today? I can't. Well regardless, the targets they did sucessfully hit were tragic enough.