Looks like your exported image (100,000 pixels square) is way too big for Google Earth.
Google Earth has limits on how big of an image ("texture") it can overlay on the map. These limits change per machine, since it's dependent on the capabilities of each machine's graphics card or chip. If you try to load an image that's too big (or which Earth can't access), then you'll see the red X instead. In Google Earth Pro (desktop app), find the "About Google Earth" menu item, where it will tell you the "maximum texture size" for your machine. Most machines these days can display images from 4096 to 8192 pixels square. Some can go up to 16384 or higher... but some older machines can only display 2048 pixel images.
If your overlays are intended for public distribution, then you'll probably want to limit them to 2048 or maybe 4096 pixels square, for compatibility with most users machines. If they are only for your own use, then you can go up to whatever your max texture size is.
There are many techniques for getting larger datasets into Google Earth, but they generally get pretty complicated, as most involve tiling the data (vector or raster), and serving the tile pyramid via a tree of Regionated NetworkLinked KMLs. There are a few tools out there for creating the raster version, often called a "SuperOverlay". If your source data is vector data, then you might also consider simplifying it and seeing if you can export it as a reasonably sized vector KML (points/lines/polygons).