3 AC current sensors using one Arduino Uno board measuring at 200Hz
Is the sampling speed enough?


It takes about 100 microseconds (0.0001 s) to read an analog input, so the maximum reading rate is about 10,000 times a second.

Ref.: https://www.arduino.cc/en/Reference/AnalogRead


Is the USB port fast enough?


The serial speed over USB is maximum 2Mbps and a fast calculation (200 samples/s x 3 sensors x 10 bit) 18kbps, so 2Mbps should be enough.