Diversified Mahindra group plans to invest USD 1 billion across business verticals in the US over the next five years as it aims to double revenues from the American market to USD 5 billion.The Mumbai-headquartered group, which currently employs around 3,000 people in the country, also plans to double the headcount over the next five years as it looks to expand operations. "We have so far invested around USD 1 billion in the US among all the businesses and we should in an interview.