120Volts (USA) x 15 A fuse.  1800watts.
you can safely load up to 80% which is roughly 1450 Watts.  Anything above you risk.

Do not forget that you may have other things on this fuse as well, it is not per socket, but per room or rooms.

RX580 Dual mine is power hungry and is using way too much. 
Try single mining and you should be ok.