Because our political parties have a tradition of using animal mascots. Elephants for republicans, donkeys for democrats, and porcupines for the (very insubstantial) libertarian party. No idea where the fuck it came from, but it's a useful shorthand in political cartoons. The statue of liberty is likewise often used to represent the concept of liberty itself, the USA as a whole, or the spirit of governance. As to why the donkey is threatening the statue of liberty, it's because some right wing nut job is projecting what the republicans are currently right now trying to do (and have been trying to do since Trump lost) onto the democrats; and that's to destroy liberty and our spirit of governance in order to retain power.
Thanks for the explanation and that's a little funny. Most places that choose animal mascots usually go with dragons, lions, bears and wolves around here. Never seen anyone choose a donkey. Elephant and porcupine are not as silly but still, you got like the whole animal kingdom along with imaginary and extinct animals to work with and that's your choice.
some right wing nut job is projecting what the republicans are currently right now trying to do (and have been trying to do since Trump lost) onto the democrats
It's bizarre. The donkey's hair even resembles Trump's.