Since USO is a proxy for oil using oil futures, I think there is a real risk of it being liquidated. Might be worth buying a few 1 or .05 puts if you can get them cheap enough. Seems like the market may be underpricing this outcome, although with oil down big again today, the opportunity may not be there. The key here will be what price you have to pay. I was trading XIV a while ago, a proxy for VIX through futures and saw this happen first hand. Any other thoughts?