The picture below is a screen capture of dxmaps.com, looking at 20 meters north America. I have long held the belief that the propagation here, in a word, stinks. I have been looking at maps like this for years, but the other day I saw this one which is especially pronounced in the difference between the northern part of the United States and the southern portion of the country.
Sadly, I have even pondered running QRO to try and overcome poor propagation. But, some afternoons or evenings, I tune across 20 meters and do not find but one or two signals. So even with some power it would still be tough to get out. Too bad I was not an active ham back in the 80's when (as the old timers say) You could load up a wet noodle and work the world.