WASHINGTON — A burger with fries is an American staple — but it seems people may be cutting back on the French fries. One of the world’s largest producers of frozen fries says it has seen a drop in demand. Food producer Lamb Weston supplies frozen fries to McDonald’s — amounting to about 14% of its sales. It closed a plant in Washington state and cut its global workforce. Some analysts say that long-term demand for fries should stay the same since it’s one of the most popular and profitable items at restaurants.