Can a cracked iPhone screen affect the touch sensitivity?

There's a crack across the middle of my screen on my iPad and the bottom half of my screen is very unsensitive (not completely) to touch.

Yup, it can even cause the screen to not work at all. Just depends on the crack. And just because it's working now, does not mean it won't stop working, So if there's anything important on the phone, you better make sure you back it up NOW, while the screen is actually working. Or you will be here later asking how to get what you want off the phone, when/if it does stop working.

The digitizer (touch sensor) is connected to the screen. That's how it works. When you repair the screen it's a package deal. Digitizer is going out so you'll need to fix soon. Best luck.
https://shop.icracked.com/collections/do-it-yourself-kits

http://www.forbes.com/...5s-screen/