How can a Cessna cut the wing of a Boeing?
An airliner wing is built to be as light as possible. Its strength is calculated to withstand the stresses of flying, i.e. lift equally distributed over the wing, bird strikes on the leading edge. 

The wing consists of one or more spars from the fuselage to the wingtip, ribs perpendicular to the spars and skin panels. All of these are made from thin aluminium: the spars (the main loadbearing structure) are a few mm thick outside the landing gear and engines. 

Fire a one-ton object into the wing at a few hundred km/h and you can do a lot of damage. Even if that object is another aircraft with similar construction. 

The damage gets worse if the wing hits the Cessna's engine block, but the accident descriptions I've seen don't say if that was the case. 

Don't assume the animation is accurate. The Cessna won't slice cleanly through the wing, there would have been a collision in which both structures are crumpled and roughly torn apart.