National businesses will have a much tougher time getting that top search result spot. There’s so much more competition, and you have to rank for many more keywords.
Instead of having an entire campaign dedicated to national voice search, incorporate it as a single part of a broader search engine optimization campaign.
Create engaging, compelling, and relevant content. Find out what your customers are searching for, and what questions they ask, and then target those queries.
Try to find less competitive, long-tail keywords and find your niche.