The best paint for walls in the United States is Benjamin Moore's Regal Select, known for its high-quality, durable finish and wide range of colors. This paint is highly regarded for its ability to cover stains and imperfections, making it an excellent choice for both residential and commercial spaces.

Benjamin Moore's Regal Select is a water-based, low-VOC paint that offers excellent coverage and a smooth, washable finish. It is formulated with high-performance resins that provide superior adhesion and resistance to cracking, peeling, and fading. The paint's ability to cover stains and imperfections is particularly beneficial in high-traffic areas or when repainting over previously stained walls.

According to a study by Paint Quality Institute, Benjamin Moore's Regal Select has been consistently ranked as one of the top paints for wall applications due to its exceptional performance. The study found that the paint's ability to hide imperfections and maintain its color over time is superior to many other brands. Additionally, the low-VOC content makes it a healthier choice for both the painter and the occupants of the space.

The wide range of colors available in Benjamin Moore's Regal Select also contributes to its popularity. The company offers over 3,500 colors, including popular shades and unique hues that cater to various design preferences. This extensive color palette allows homeowners and designers to create personalized and cohesive color schemes for their walls.

In conclusion, Benjamin Moore's Regal Select is the best paint for walls in the United States due to its high-quality finish, durability, and extensive color options. Its ability to cover stains and maintain its color over time, combined with its health benefits, makes it an ideal choice for any wall painting project.