Systems get entangled with each other by interacting. So entanglement cannot "propagate" faster than the fastest possible "mediator" of an interaction, which is the speed of light.
The "instantaneous" aspect comes up in entanglement and measurement. Say you start off with an entangled pair of electrons A and B in your lab, and measure electron A. Measurement is an interaction, so you become entangled with the electron. By knowing the initial entangled state and your reading of electron A's state, you can know stuff about the state of electron B at the time of the measurement, even if electron B has traveled a very long distance in the meantime.
I personally find this point of view nicer than assuming that I somehow collapsed electron A's state and caused an instantaneous remote collapse of B's state.
The "instantaneous" aspect comes up in entanglement and measurement. Say you start off with an entangled pair of electrons A and B in your lab, and measure electron A. Measurement is an interaction, so you become entangled with the electron. By knowing the initial entangled state and your reading of electron A's state, you can know stuff about the state of electron B at the time of the measurement, even if electron B has traveled a very long distance in the meantime.
I personally find this point of view nicer than assuming that I somehow collapsed electron A's state and caused an instantaneous remote collapse of B's state.