Fly by wire is about removing the weight and complexity of mechanical control systems. A pilot wouldn't likely have the strength to move the controls without fly by wire. However, I don't think that's what you are asking. Fly by wire does not inherently have to be computer assisted; it could simply translate your input to a control surface movement without interpretation. Of course, to get any kind of feedback, it is going to have to be computer generated. The question is where to draw the line.

Finally, you compared Airbus to Boeing. Both are fly by wire. The difference is, I guess, that the control yokes on Boeing are mechanically linked to each other but not on Airbus. However, from the yokes to the control surfaces is fly by wire either way. My understanding is that the difference is in philosophy of how much the computer does for you.

I hope I got all this right.