Technically, you can be here in this country and legally working and not be an American citizen. They're legal immigrants. That's why we have the distinction.
I believe at the time I heard that the World Trade Center attacks caused the deaths of the most British citizens at one time since the Blitz (London, WWII).
So, while I understand your claiming of the disaster as an American tragedy, the sorrow and loss was legitimately felt by many other nations' losing their own citizens, too.
ETA: for example, from CNN, 9/13/01
http://cnnstudentnews.cnn.com/2001/f...attack.latest/
# Nations across the globe are reporting dead and missing in the U.S. terror attacks. British Foreign Secretary Jack Straw said Thursday at least 100 British citizens have been confirmed dead in the U.S. terror attacks. Acting Australian Prime Minister John Anderson said three Australians in New York have been confirmed dead and about 75 were still missing. Japan reports that it has 100 nationals still unaccounted for. Twenty-seven South Koreans were listed as missing. One Korean was on the hijacked United Airlines plane from Boston. Notimex, the Mexican news agency, is reporting at least 12 Mexicans cannot be accounted for. There were 100 to 150 Mexicans working at the World Trade Center.