If you are buying agency services in the United States, three things matter more than any vendor list: where the capability actually sits, what federal and state rules require of your campaigns, and whether the agency can show evidence for the claims it makes. This guide covers all three, cites its sources, and links to our US listings so you can move from reading to shortlisting.
How large the US agency market is
IAB and PwC report that US internet advertising revenue reached nearly $300 billion in 2025, a 13.9% increase year over year, with social media up 32.6% to $117.7 billion and digital video up 25.4% to $74 billion. The prior year, 2024, came in at $258.6 billion, up 14.9%.
Source: IAB/PwC Internet Advertising Revenue Report, Full Year 2025, 16 April 2026. www.iab.com/insights/internet-advertising-revenue-report-full-year-2025/
Source: IAB, Full Year 2024 results, 17 April 2025. www.iab.com/news/digital-ad-revenue-2024/
What this means for a buyer: budget is concentrating in social, video and commerce media, so the agencies with genuine depth in those channels price accordingly. When a proposal is much cheaper than its peers, the difference is almost always seniority, hours or subcontracting — ask which.
Where the capability sits geographically
New York remains the densest market for brand, media and PR, with Los Angeles and the Bay Area strong in creative, entertainment and technology work, and specialist ecommerce, retention and SEO shops spread across Portland, San Diego, Chicago, Austin and the East Coast. In our own US directory, listings cluster in New York, Los Angeles, San Francisco, Portland and San Diego, with several fully distributed teams that publish no headquarters city.
A distributed agency is not a weaker agency. What matters is time-zone overlap with your team, whether senior people join calls, and whether they have run campaigns in the market you are targeting.
Domestic versus cross-border work
US buyers frequently hire Canadian and UK agencies, and US agencies sell into both. If you are buying across a border, confirm the contract currency, who carries exchange-rate risk, where the work is performed for tax purposes, and how personal data crosses jurisdictions.
Rules that shape US campaigns
FTC endorsement and advertising claims
The FTC''s Endorsement Guides govern testimonials, influencer content, reviews and affiliate arrangements, including how material connections must be disclosed. Objective performance claims need substantiation before they run.
Source: Federal Trade Commission. www.ftc.gov/business-guidance/resources/ftcs-endorsement-guides-what-people-are-asking
Ask candidate agencies how creator disclosures are written and monitored, who reviews claims before launch, and who holds the substantiation file.
CAN-SPAM and commercial email
Commercial email to US recipients must meet CAN-SPAM requirements on sender identification, subject lines, a physical postal address and honouring opt-outs.
Source: Federal Trade Commission. www.ftc.gov/business-guidance/resources/can-spam-act-compliance-guide-business
State privacy laws
Comprehensive state privacy laws keep coming into force on a rolling basis; a further slate of California measures plus comprehensive laws in Indiana, Kentucky and Rhode Island took effect on 1 January 2026. Requirements around targeted advertising, opt-out signals and sensitive data vary by state.
Source: IAPP, 5 January 2026. iapp.org/news/a/new-year-new-rules-us-state-privacy-requirements-coming-online-as-2026-begins
Source: IAPP US State Privacy Legislation Tracker. iapp.org/resources/article/us-state-privacy-legislation-tracker
Ask any agency proposing paid media or lifecycle programs how they handle opt-out preference signals, audience matching and consent records across states.
What to ask before you shortlist
- Which named people will actually do the work, and what percentage of their week is yours?
- Show two engagements similar to ours in scope and budget, with the outcome and a client contact who can confirm it.
- What is the minimum engagement, and what does it buy in the first 90 days?
- Which parts of the work are subcontracted, and to whom?
- Who reviews advertising claims and creator disclosures before they run?
- What happens to ad accounts, creative files and data if we leave?
What to treat as weak evidence
- Awards with no named jury, year or category.
- Client logos with no described engagement.
- Directory rankings you cannot trace to a published method.
- Case studies with percentages but no baseline, timeframe or attribution method.
- Guaranteed positions, rankings or lead volumes.
How we assess agencies
Every agency on this site is scored against a published 100-point method covering demonstrated results, verified review quality, specialty depth, portfolio relevance, client and industry fit, team expertise, and transparency. Scores are provisional where evidence is missing, and we show that rather than hiding it. See the methodology at /methodology and the US hub at /countries/united-states. You can filter the full directory at /agencies.
We do not copy listings or ratings from other directories. Facts on agency profiles come from the agency''s own site or named press, each with a URL and a retrieval date.