What rating should a spade electrical connector have to power an eTopxizu 12v Dc 30a 360w Regulated Switching Power Supply from a US wall outlet?
360 W at 120 V will draw 3 A on full load. (From P = V * I)

Connect with an inline fuse in the L wire and make sure you connect the earth / ground lead.

Any forked or ring terminals that fit that size screw are likely rated for 3 A or more. If all the strands of your mains lead wires fit inside the crimp barrel it's a good sign that all is well.