It would be very strange if American weapons weren't used in a conflict this big, which is a very different question from "did the US government sell weapons into this war".
Guess you are on the wrong side of things if you know your weapons are getting laundered through other countries to get to a conflict. And of course uk, us and china know this and always knew this.
I've looked for articles and don't see anything about US weapons. It would be very strange, indeed, but supposition isn't proof and I can't find anything suggesting the US is involved in anyway. Colour me surprised, tbh.