I won't talk about the merits of huge fines being an approach to solving competition, but from the inside I can see a few ways that the EU pale:
1. While the EU operates as a body for rule setting, the individual members are still highly autonomous in a way that doesn't compare to the types of collaboration that's possible across states in the USA. This is worsened by language divisi
ons.
2. Internally each country is trying to foster their country as the place to be to launch a "start up", but that fragmentation is almost certainly slowing down the formation of a European equivalent to silicon valley.
3. There isn't a competitive investment funnel to what's available in the USA and the USA benefits from "network effect" style advantages purely from being further down the road. So if someone in the EU has a good start-up concept, chances are they'll try to make it work with the big guns in the USA, or cash it out to a US entity.
4. The EU is incredibly shortsighted in allowing the sale of important tech companies to foreign entities (primarily US-based entities). Many of the bigger advancements of today started in Europe.
5. Similar to points 3+4, companies in the USA are often able to build more value with the IP they develop or acquire (on account of numerous factors including some inconvenient ones). So even when a EU start up has a good product it may not necessarily be as successful due to those factors.
6. The EU tends to write ambiguous legislation that is open to interpretation and at worst: intentionally vague. While some believe this is just trap setting for collecting fines, the consequence of vague rules is a loss of appetite to develop in that market. English speaking markets tend to have much more specific legislation and their governments are available to offer specific guidance. This is something that the EU lacks and a frequent complaint from the likes of Google et. al.