When I was a kid, my mother taught me to use my fork in my left hand and my knife in my right, because it would be easier for me to eat at a table with other people if I wasn't trying to do it backwards. She made a brief attempt to teach me right-handed spooning, but I was never co-ordinated enough not to spill the soup in my lap, so I use the spoon in my left hand, and was taught to keep my elbow as close to my body as I could so as not to run into everyone! If I'm picking up a knife to use by itself (eg. to spread butter or make a sandwich) I'll use my left hand, but I cut my food with my right.
Eating American-style seems particularly silly to me as a left-hander. (I'm Australian and even though I live in America I've never found any reason to change my lifelong habit.) But I wonder how American left-handers eat? Do you pick up the knife and put it down at every bite and use your fork in your right hand because that's what everyone else does? Or do you pick up the fork in your left hand and still put the knife down when you don't really need to?