Does An automotive fuse box generates 20 amps of power?

No, an automotive fuse box doesn't *generate* power. It's a distribution and protection device. It doesn't produce electricity; it simply routes the power generated by the alternator (and possibly the battery) to various circuits in the car. The fuses within the box are rated for different amperages (like 20 amps, 10 amps, 5 amps, etc.), protecting those circuits from overloads. The box itself doesn't have a single amperage rating.