On a train trip across the US two years ago, my coffee came with a stick-shaped sachet of milk creamer from Lakeland Dairies, the cross-border co-operative headquartered in Cavan.  At the time, Colin Kelly was getting his feet under the table as Lakeland’s chief executive. He had just moved across from Ornua, where his career trading Kerrygold butter and managing strategic risk had focused on the North American market. The logical opening question for our interview this week concerned the impact of US tariffs.  The co-op’s long-life milk sachets are ubiquitous on American hot drinks trolleys. “If you were on…