If there are too many devices plugged into the computer USB will it affect the whole machine?

Too many computer USB devices will not affect the computer.

Instead, it will increase the functionality because of the increase in peripherals. The USB port is designed to take into account the increased functionality of the peripheral applications. So there is no need to worry at all.

And the power supply of most computer configurations is set at less than 60% utilization. USB output for each port is 5V, almost no pressure. Please feel free to use it.