For more mountainous or thick forest areas this is understandably. It required combustion engine trains, simply because of steep mountains, where it's difficult to put down power lines or forests with a lot of trees who can easily destroy power lines. USA however is mostly flat. Looking at some like Austria or Swiss, if I see this correctly, they also are on a good way. Here we have a lot of hybrid but in general our train transport is a mess of mixed.
I think the original poster posted this intentionally as sarcasm because there is so little color in the image. If you look at the original image and look at the USA North east near new york, you'll see a few meager lines that are various colors (as well as a few slivers in south and central america, and what looks like a dot in los Angeles). This is showcasing just how little electrified rail exists in the americas.
It may not seem like it, but it is actually in color. I'm on mobile and am able to see it. If you're not able to, it may be an issue with your app or method of viewing the post.