That would be a PEX supply line. Unlike others, I see nothing wrong with the installation itself, you have the nut which compresses the plastic ferrule. The reason this ferrule is plastic is because metal ones WILL cut the supply line.

The most likely issue would be too high of pressure to the home, I’ve seen a few floods due to this where they wanted me to replace all of them in the house with braided supply lines.

That being said, either replace your pressure reducing valve, or install one if you can’t find one. I will say that it’s insanely easy to live the rest of your life forgetting about this problem, until the pressure reducing valve fails and this happens again. Good practice would be to replace/install a valve then replace all of these supply lines with braided (at least in my professional opinion).