No, Mistle Thrush is mostly not a goth band, but on some of their albums they played Ethereal Wave, which is a core subgenre of goth music. Albums like Agus Amàrach are examples of their goth sound.
One of the other goth artists that is similar to them is Speaking Silence.
Mistle Thrush is located in United States, Massachusetts, Boston, active in 1993 — 2002. You can find more information about Mistle Thrush on their GothDB band page.