I'm sorry but I believe that Maryland and Louisiana would disagree about your statement of the only states to suffer a foreign attack. Little thing called the War of 1812.
Seem to recall the British burning down DC and Baltimore.
I sit corrected, technically...my statement had more to do with an unexpected sneak attack like Pearl Harbor.
The British sacked Washington but didn't get into Baltimore. They were stopped by the Americans at the Battle of Baltimore.
Check out: http://www.galafilm.com/1812/e/events/wash_ambalt.html