1. The importance of use
The main difference between EU and US systems is that actual use of the trademark is very important in the US when acquiring trademark rights. In Europe, it is not important at all (although if the trademark is descriptive, it can acquire sufficient distinctiveness through its use). In EU you can register a trademark without ever having even an intention to use it. In the US the registration requires that you can prove that the trademark has been used. Also maintaining trademark rights in the US requires use. When trademark registration is renewed (this is done every 10 years), evidence of use must be submitted. In EU the the registration and renewal only requires the payment of fees.
The significance of use is also manifested in more fundamental way. In the US it is possible to acquire trademark rights by merely using the trademark and without registering it (although these rights are more limited than for registered trademarks). EU trademark rights can only be acquired by registration. Some EU countries acknowledge trademark rights based on the use of the trademark, but the threshold to have such rights acquired is typically very high. Mere use is not enough, some degree of recognition and good will is required.
2. Examination of the application
Although the process is very similar in the EU and US, there are three significant differences between the EU and US trademark examination.
The first one is that the US trademark office examines prior registrations, and if it considers that there are similar prior trademarks, it will not allow the registration. The EU trademark office, by contrast, only examines the distinctiveness of the trademark, but not prior registrations. It will not refuse a registration because somebody has a similar trademark. To safeguard prior trademark owners' rights, they have the possibility of opposing applications that they consider infringing.
The second difference relates to the kind of marks EUIPO and USPTO consider registrable. In general, the EUIPO has a higher threshold for considering trademarks “distinctive” and capable of being registered. This is not mere technicality. It means that many trademarks that have been registered in the US cannot receive trademark protection in the EU because the EUIPO considers them “descriptive”.
The last difference relates to identifying the goods and services in the application. EUIPO accepts broader and less specific terms than the USPTO. For example, EUIPO considers "software" an acceptable term whereas the USPTO requires that the nature of field of use of the software is included (for example, "Music-composition software").
EUIPO has slightly higher government fees than USPTO. For example, the government fee for a trademark application in 3 classes is 1050 EUR, whereas in the US it is 825 USD. That in itself is not worth the mention.
The cost issue is worth mentioning because there is a whopping difference in the EU and US in opposition costs. The cost of an opposition in the EU is rarely more than 5000 EUR. According to International Trademark Associations 2013 study the cost of an US opposition was a whopping $150,000–$500,000. In our experience a typical opposition process costs at least ten times more in the US than in the EU. The opposition process in the US resembles litigation with extensive discovery whereas in the EU it is more straightforward and completely a written process (in theory oral proceedings are possible but in practice they are extremely rare).