There's a ton of single threaded performance problems in Google Earth Pro if you watch its activity closely, when you have something like 150MB-300MB of KML placemark lat/long locations and lines loaded. Moving to a new geographic area will cause it to re-read the entire KML for an area and render the placemarks/lines onto the map using *only one CPU core* no matter the capability of your system. There's tons of other things it does with only one core.

Load the fiber maps for a facilities based ISP that spans a few county size up to a whole state size of scale, with good granular detail (like splice case and pedestal locations, etc) and watch Google Earth Pro slow to an absolute crawl even on a $599 current gen Intel core-whatever or AMD Ryzen single socket workstation CPU.

To be fair to it, people are trying to do all kinds of things these days with KML files that it really wasn't designed for, or ever intended for, and are much better done with professional grade GIS software.