The current U.S. regime is also replacing some amount of that legal certainty with regime fealty. Picking Chinese options over American ones probably runs a risk of upsetting their leader. I've got to imagine American companies are weighing this factor in their decisions.
Regime fealty has always been there in US. The current admin is just more corrupt and throughly incompetent at hiding it.
That's certainly one factor, yes. But even before getting to that part I think the bigger issues for Big Corp legal teams is mostly around the legal ambiguity of the models themselves. What representations are made about the training data? What jurisdiction governs the license? If somebody alleges that the model infringes their IP, what rights does AT&T have?
Counterparty risk is a lot more straight-forward to evaluate when dealing entirely within the US, with US companies.