In non-async Python, generally the thing that blocks is a thread -- something Javascript doesn't even have! A different thread will happily run in the meanwhile.
Right, but some other JavaScript on the same thread will run while a different piece of JavaScript is awaiting. That's why JavaScript can get away with not having threads. Also- any number of background threads will be running at any given time to read data off of disk, load and process network requests, load data from a DB, delegate commands to system processes, etc, in true parallel with the JS code. When one finishes, it'll put an event on the event loop and JS will pick it up when it gets the chance.