But they did so because the European owned banks were active in the US serving US customers (and solvent enough to repay) which is why they had the dollar oblig

But they did so because the European owned banks were active in the US serving US customers (and solvent enough to repay) which is why they had the dollar obligations they needed to borrow to meet in the first place. Argentina or Panama having a bit of an economic slowdown whilst the US is growing nicely isn't the Fed's problem: the monetary policy decisions will only take into account to the monetary policy needs of the US, and it's not particularly in the interests of the Fed to bail out Argentine bank reserve shortfalls unless the contagion is likely to hit the Us either.