What's top fast-food chain in country?

Depends on whether you're looking at number of locations or amount of sales - and, to be clear, we're talking both "fast-casual" and "quick-service." QSR, a trade magazine (short for quick service restaurant), offers a chart of the top 50 in the country; you can sort them any way you like.
Highlights: McDonald's easily tops sales, though Subway has the most units. Starbucks places third and Burger King fifth either way you look at it. Chick-fil-A - which is 21st in number of units and 10th in sales totals - tops the sales-per-unit category, handily beating McDonald's.