Listen to a reading of this article (reading by Tim Foley): During an appearance on ABC’s This Week with Jonathan Karl, Secretary of State Tony Blinken explicitly said that the US would not oppose Ukraine using US-supplied longer-range missiles to attack deep inside Russian territory, a move that Moscow
I remember reading that AFU couldn't pull the trigger on HIMARS without US approval. If other US/Nato weapons systems are sold under the same rules that escalates this conflict well beyond the status of proxy war.
US and AFU weren't exactly shy about the fact yankee drones and satellites are providing targeting data for the missile strikes. The only reason everyone pretends it's a "proxy" war is because Russia can't openly declare against NATO (due to nukes)