If you're too frightened or flat-footed to sign up for military service, there are still many ways you can show your patriotism so your neighbors don't start to doubt you and turn you into Homeland Security or INS. Nothing says "I love America" like a competitive hot dog eating contest, a three-legged race or oohing and ahhing over Chinese fireworks falling around Lady Liberty, a French statue.
Just remember to buy American beer and to invite only your friends with valid green cards.