Sure, in theory, an appraiser can go anywhere, and with the right set of circumstances be able to do a competent appraisal ( fingers crossed they did not miss something ) The question as asked makes it easy to say yes, I could competently appraise anywhere given the set of conditions ( assumption).
But to believe that set of conditions would be present in the SFR regular assignment example used is absurd. Direct order lenders use a panel of local appraisers and AMC's use their panel/staff, both want the report back fast, and MLS is regional $ membership subscription. Yet for this assumption, a mythical client sends an appraiser to a far off location for an ordinary res assignment ,allows lots of time, and appraiser magically has access to local data ( MLS) .Poll result allowing multiple choices is overall answer that geo competence not needed (143% + out of 100% but who's counting..)
I asked the question in the abstract because i'm trying to suss out the underlying fundamentals, which are significant to the extent that if a concept is true it will hold up consistently across a wide range of specific situaitons rather than just a couple of them. In general, the specifics tend to be an expression of the fundamentals.