BALTIMORE — It’s a big world, and it takes a big firm to help people negotiate the international legal system. And for many large U.S. firms, expanding their pro bono efforts to the global community has become just another aspect of the practice. At Miles & Stockbridge P.C., international pro bono work ranges from assisting foreign citizens in the U.S. to helping Americans who find themselves in legal predicaments overseas, said Stephen J. Cullen, a principal at the firm. “Say you’re a …