It is junk, but "space junk" has a very specific meaning [1] and this is not it. Pretty much all rocket launches have debris designed to fall back down into ocean, some recovered and some not. Not only that, but defunct satellites are intentionally crashed into the ocean and left there [2].

There is literally nothing special about this part other than perhaps it floated and ended up in another country.

[1] https://en.wikipedia.org/wiki/Space_debris

[2] https://en.wikipedia.org/wiki/Spacecraft_cemetery