As of my last knowledge update in September 2021, the United States is home to numerous digital marketing companies that offer a wide range of services to businesses across various industries. These companies provide services such as SEO, social media marketing, content marketing, PPC advertising, web development, email marketing, and more. Keep in mind that the landscape may have evolved since then, so it's advisable to conduct thorough research to find the most up-to-date information. Here are a few notable digital marketing companies in the USA:

1. Ignite Visibility (San Diego, CA): A full-service digital marketing agency known for its expertise in SEO, PPC, social media marketing, and web design.

2. WebFX (Harrisburg, PA): A performance-driven digital marketing agency offering services in SEO, content marketing, and web design.

3. Thrive Internet Marketing Agency (Dallas, TX): Provides services in SEO, web design, social media marketing, and PPC advertising.