If someone is drawing 120w - 1 amp - your only control as a power source is to try to lower the voltage (voltage potential). Problem one: that will go out of spec with what devices expect, if you try to provide 80 vac instead. Problem two: switch mode power supplies that can handle sagged voltages will just try to draw more amps to get the same net power.

There's really not a good way to "cap out" power. The device just sees voltage potential (volts) and doesn't know to go lower. Blowing a fuse is the only real indicator we have.