Hello and welcome GunSgtHighway !
Made some races with AI and those are well made tracks ; roads are not too large and neat, AI behave correctly, and I particularly like your efforts for scenery on your first track and the neat kerbs you made on your 4th track. Hmap ramp in your 2nd track is well made too. Technically there's no problem.
What bothers me is that there's no sunk tires, or sand area in the inside of corners to tells us precisely where is the limits of the track, if we can chew a little on corners or not ; as with your tracks I can make very tight lines on many corners and overpass easily the AI that stick to the road. I don't know if it was your intention. If not you can add sand, or sunk tires inside corners but let the checkpoints as they are ; players who wants to cut the corner would be slowed down and would not have an unfair advantage if they choose to do this, but still they could complete their lap. Or you may even add haybales, walls, bushes, trees, but with sunk tires or sand it's better as they only slowed down players instead of being totally stopped and even damaged with walls or objects.
Scenery is lacking somehow, with only few stands and trees around. It's quite dry visually, or simple if you prefer. It's time consuming to build a proper scenery and think about what to place and where but it's really worth it, as your tracks may be way more appealing. Of course it's more difficult when you have a large world size. Personally I like WS100 or below because we see well our car but the layout can still be good enough and varied and objects are bigger, so less to place and they fill the emptiness quicker. You may use Gimp, Photoshop or even Paint to do the Lmap, like making grass more real by adding soft dust/mud touches to it, and mix tarmac colors on your roads. There's plenty of tutorials for that, many call this technique "dithering".
Apart from those points they are well made tracks and I encourage you to keep going.