I see this as two separate questions. If other governments stopped intervening, the material for war would be much more scarce and both sides would reduce the rate at which they expend it. I suspect they would pursue less violent resolutions to their disputes.

The trade point would mean placing a full embargo on both nations (until hostilities cease, I imagine). Typically, embargoes don't achieve the stated aims of those who enforce them. Regimes are usually strengthened by embargoes, because it's an external force for the public to unite against. That scenario would not go well, in my estimation.