The leaders of U.K. and international law firms have come to expect and, one suspects, dread the question they hear most often when they discuss their global growth and ambitions: “What about in the United States?”

Most responses over the years have opted for one of two approaches. The first is to talk about “organic growth”—incremental hires of individual lawyers or small teams from domestic U.S. firms, usually in New York or Washington, D.C. The second is a euphemistic reference to “more dramatic opportunities”—mergers.