This doesn't look right:
Bridge.begin(9600);
Serial.begin(300);
Bridge.begin() is normally called with no arguments. It can be called with a single numeric argument, like you now have it, and that would be the baud rate that the serial port talking to Linux should use. It's there in case you have a special requirement to use a different baud rate. But you can't change it here unilaterally - if you provide a custom baud rate here, you need to go into Linux and change the baud rate there as well. If you change it only in the sketch, then the two processors will not be able to talk to each other. Bridge.begin() will not be able to establish communications with the Linux side, and it will likely never return. This is probably why your LED is no longer working, because Bridge.begin() has not returned while it tries over and over again to establish communications.
Then, you have the baud rate in the Serial.begin() call. 300 baud is a valid speed, but it is very slow. I doubt you really want to use that low of a speed. The only reason to do so is if you have a VERY long serial cable (hundreds of feet?) or you are using a dial-up acoustic coupler modem (has anybody used them in the last 40 years or more? The last time I used 300 baud was in the mid-'70s with an acoustic coupler - where you manually dialed the telephone and placed the phone handset in the rubber cups of the modem. This was when ARPAnet, the precursor to the Internet, only had about a dozen computers connected to it, and I had to dial into Rutgers to get onto it, because my university wasn't connected directly.)
Cool! I found a picture of the same Anderson Jacobson modems I used in the '70s. 8)
Talk about a trip down memory lane...
Anyway, back to the topic... I think you need to take the parameter out of the Bridge.begin() call, and use a more appropriate value for Serial.begin(), like 9600, 19200, or 115200.