Dynamically populating select input fields using jquery $.load and twig template
Your code looks fine and worked for me when testing locally. However it could be failing due to the fact that you're not url-encoding the parameter before you send the request. If the values contain spaces or other special characters, for example, this would make it fail. To fix that issue, try using encodeURI() like this:

$("#second-choice").load("{{ distUrl }}data.twig?brand=" + encodeURI($("#first-choice").val()));


This works for me when testing with values that contain spaces at least.