If I have a hammer (A* search), every problem (TSP) is a nail (pathfinding).
Yes, in theory it's possible to transform the TSP problem into a much bigger graph and use A* search on it. But regrettably it's useless because it won't scale (see spinning_plate's comment). Even small instances might take years to solve that way on modern hardware.
TSP is NP-complete, pathfinding isn't.
If it's screw (NP complete problem), use a screwdriver (metaheurstics, ...).
Use algorithms such as metaheuristics (tabu search, genetic algorithms, simulated annealing, ...). For software examples, see Drools Planner, openTS, jgap, cpsolver, ...
