Overloading buck regulator
Does same thing happen if I use a linear regulator instead, meaning output voltage drop during overloading? 


Everything drops in output voltage when the current gets too high. If it did not you would have a perpetual motion machine that produces energy from nothing.


  Can someone help me understand this by assuming let's say I have a 3.3V buck regulator circuit that is rated for up to 2A. What happens to the buck topology components' voltages/currents when the load tries to pull 3A instead that causes the voltage output of regulator to drop?



Inductors saturate when the current gets too high and they stop doing their inductive thing
Transistor switches saturate and can't pass more current to the output.
Any and all resistances in the current path will produce increasing voltage drops as current increases to the point where they output voltage as dropped intolerably low.
The capacitor is too small to supply enough charge to "tide things over" for the frequency at which the converter is operating at; The frequency being how often that capacitor is topped up.