It's difficult to provide a definitive list of the top digital marketing companies in each country, as the industry is constantly changing and new companies are emerging all the time. However, here are a few examples of some of the top digital marketing companies in America, India, Japan, China, and the UK:
America:
1. Ignite Visibility
2. WebFX
3. Disruptive Advertising
4. Thrive Internet Marketing Agency
5. SocialSEO
India:
1. Webenza
2. iProspect India
3. Adlift
4. WatConsult
5. Performics India
Japan:
1. Dentsu Inc.
2. CyberAgent, Inc.
3. Pairs Co. Ltd.
4. Mediamath Japan K.K.
5. Rakuten Marketing Japan
China:
1. BlueFocus Digital
2. Tencent Advertising
3. Dentsu Aegis Network China
4. iClick Interactive Asia Group Limited
5. Social Touch
UK:
1. Jellyfish
2. Koozai
3. Ignite Digital
4. Hallam Internet
5. Impression
It's worth noting that this list is by no means comprehensive and there are many other excellent digital marketing companies operating in each country.