The challenges posed to the rand by the US policy uncertainty clearly fall into the category of portfolio shocks. Here, literature tells us that policymakers should respond to these shocks by tightening monetary policy.
In an inflation-targeting framework, the tightening would depend on the extent to which the weaker exchange rate was expected to impact on inflation rather than acting to protect the exchange rate per se. The role of inflation expectations (and monetary policy credibility) would be central to this.