I have posted before about how the US seems to have a bewildering assortment of plugs for domestic equipment. Here we have just one.
We only have 1-the Edison with 3 pins-hot-neutral and ground. However it is available in 2 configurations-the 20A (which you can plug a 20A plug or a 15A plug) and the most common standard 15A.
Decades ago you could find 2 pin edisons (no ground), but they are rare these days (only in older buildings).
You find this in all the houses-businesses etc. You can plug ground or ungrounded equipment into them.
However once you get to 20A or more-it all changes. There start to be all kinds of varieties-120V, 240V, twistlock straight pins-different combinations of straight pins etc.
You mentioned the shutter on your plugs. Do your "wall warts" or line lumps" all have 3 pins? Most of ours do not have a ground pin. It is the rare one that does have a ground pin.