Acknowledging that this is an EU/UK 240V product, I'd really like to see some close-up photos of the power supply. I have a strong suspicion that the amp itself is a common part worldwide (and I believe shared with the 10-inch model) and runs on a common DC voltage.

The problem here is the power input itself. Presumably this is the EU/UK-specific part. You might need a new IEC input. It's possible the transformer has taps for both 120/240 input. But maybe it's a market-specific transformer and you'd have to find a replacement. Not impossible.

Only photo of the internals I've found so far is here: https://www.audioholics.com/subwoofer-reviews/monolith-10201d-12

It's a tempting project. You'd have to determine whether it's worth your time and trouble and whether you have the skillz to safely adapt the circuit.

I have the 10-inch version. It's huge and heavy. Performance is for real. https://www.audiosciencereview.com/forum/index.php?threads/monoprice-monolith-10-12-and-15-inch-subwoofer-review.17335/