Arduino uno not recognised by computer and reset button doesn't work

So, for my final project, I was making a stoplight that would change colors based on timings set by the user. So, the first time I uploaded the code, it worked perfectly. The remote controlling between my Arduino Nano and my Uno was working well. I decided to move the Uno across the room to make sure it was working, and in turn had to plug it into a power supply, that is plugged into a 12V 1.5A AC transformer. The powe supply is the mb102, and the Uno is plugged into it via the USB. After that, it al went to crap. The nano loses its code whenever I unplug it from power, but resetting it works fine. As for the Uno, it stopped working completely. When I plug it into my laptop, I get a windows popup saying "USB device not recognised," and the power and TX lights are on, steadily. When I press the reset button, nothing happens. I think it may have something to do with the power supply, because when I plugged in two of my Arduino Nanos, they stopped working as well.

Attached are my circuits-- the transciever on the reciever circuit is wired the same as the one on the transimitting circuit, it just takes to long to make it look nice.

Any suggestions are helpful,

Some models of MB102 have an input rated for 6V to 9V DC. Others are 6V to 12V DC. If your power source is, as you said, 12V AC then I suspect the MB102 is no longer working. You should check it with a meter.

I think I may have found a source of the problem. It has two output settings, 3.3V and 5V. I tested both. 3.3V outputs as expected, but 5V is outputting 14V. Would that have killed my arduino UNO in the circuit attached, though?

5V is outputting 14V. Would that have killed my arduino UNO in the circuit attached, though?

Yes, it could certainly have killed your Arduino.. ABSOLUTE MAXIMUM on the Arduino's processor chip is 6V.

I have around 20 of the power supplies, so I decided to test some scenarios.

With a 9V battery, they all did as they were supposed to.
With the 12V AC transformer, they all worked. Then I accidentally shorted one of them, and BOOM, 14V all the time when it was supposed to be 5V.

I guess that solves that.

I'll need a new arduino now.