I don't see a single thorn in the images you provided.
It does look a lot like the invasive species that may go by the name Fallopia japonica now, and has been termed Japanese Knotweed and other common names. I don't believe this species is known for having thorns.
This plant can create huge masses via underground colonizing behavior, and especially likes riparian zones within which to spread - but doesn't necessarily require such conditions.
The seed panicles have fairly sharp bristly bits which can easily be taken for thorns when dry in autumn. And the stems are starting to rot down for the winter now. Sorry, but this absolutely is Japanese Knotweed. I know it far too well.