How can I open a Google Maps URL in Apple Maps? Is there a way for me to convert a Google Maps URL to an Apple Maps-friendly format so it opens in the correct place?

I might be in the minority, but where I am, Apple Maps offers vastly superior driving directions.
You can simply copy and paste an URL from Google Maps (either from sharing with the Google Maps app), paste it in the Apple Maps search bar and it will resolve the correct location.

Google Maps short URL (of the form goo.gl) won't work and will need expansion before proceeding.

I've created myself a Workflow (soon to be named Shortcuts in iOS 12) to expand the URL automatically. You can force-touch an URL going to Google Maps and use this Workflow with the Workflow share extension.