Not really.
If you're in C and there's an A7 chord,then technically at that point you're in D,A7 being the dominant of D,but more often than not it's used as a tonally different colour,while still being VI of C.Stick some extensions on and the interchangeability is more obvious.
A7b10,b9,b13 gives a flatter tonality more akin to C.See?