I want to tear up my food instead of using a knife
Why don't you want to use a knife?
It would be much more fun to tear up the food with my hands.
I think that is highly inappropriate in the US. With some types of food, like bread, it is okay to tear it. You can probably do what you like in your own home, but out in public you should conform to standards.
I just want to do it.
I can understand that, but you should try and conform to the customs of the culture you live in. In your own private house, you can do as you wish. Try to be more accomodating to others.