No, they are nothing alike touchscreens. The whole and only point of a touchscreen is that you touch the actual visible thing on the screen (you touch the screen). Track pads, as good as they are, have 0 to do with that.
Just imagine if they offered a Mac without a keyboard, just the trackpad and the screen.
I wouldn't say they're nothing alike. The gestures developed for MacOS and the trackpad are paradigms derived from iPhone touch screens - swipe, pinch, zoom, tap to click (if turned on). And for the Mac, cognitively, at least with the cursor, the trackpad surface maps intuitively into the area of interest on the screen.
I agree, typing on a trackpad "keyboard" would suck, but on a Mac w/ a built in keyboard, that's superfluous. And who actually enjoys typing on an iPad on-screen keyboard?
Just imagine if they offered a Mac without a keyboard, just the trackpad and the screen.