In a world at that scale that much debt held by one single entity is massive. Activist investors have taken over large companies on such a small amount.

I'd be careful undervaluing the influence that a single debt holder of that size could have. Plus you are further assuming that that's the totality of their influence and it's likely 2-3* that if you include influence.

I'd definitely be wary if I was going to war (trade is the new war) with another nation.