If it really was such an important safety issue, then the relevant UL and/or CE standard would require it. Neither UL or CE does (has anyone seen a washer, dryer, dishwasher, iron or electric stove with a built in fuse? I have not), and that in and of itself says that the level of stupidity required to make this error is very high. The only place I am aware of where it is a requirement is the UK, where most plugs are required to have a built in 13 amp fuse. I am not aware of a similar requirement anywhere else in the world. Most of the power supplies that have a built in fuse, are also designed for operation at either 120 or 240 volts, switch selectable, so on these devices it is an error that isn’t difficult to make. For most devices however, this is an error that requires considerable effort to make.
By definition a 120V plug will not fit into a 240V socket and vice versa. That is no accident either. So in order for this to happen, someone has to have messed up very badly either by attaching an incorrect plug, or using an incorrect socket for the intended voltage. UL does take safety very serious (CE much less so). I have built UL listed products, and the standards are indeed stringent. You even have to be careful about the direction of air flow in many products, and the articulated finger test can be a real nightmare.