Lone Star Planet by H. Beam Piper audiobook.
New Texas: its citizens figure that name about says it all. The Solar League ambassador to the Lone Star Planet has the unenviable task of convincing New Texans that a s'Srauff attack is imminent, and dangerous. Unfortunately it's common knowledge that the s'Srauff are evolved from canine ancestors—and not a Texan alive is about to be scared of a talking dog! But unless he can get them to act, and fast, there won't be a Texan alive, scared or otherwise!