Looking for clarification: Flying helicopters commercially in Europe with an FAA cert
 

N reg OK and US operator OK but the operator would need cabotage rights and freedom of the air rights.

You would only expect it to happen if the local commercial operators were not capable of it. Unless that is the case - I doubt it would happen.

EASA tickets require rights to work and live as well - another stumbling block some of the time.

It´s pretty complicated and quite frankly not worth it unless you have a pretty good job lined up with an operator.

There are 14 (fourteen, I kid you not) EASA theoretical tests required. Might be a few less if VFR only. Then you can start training for the CPL skill test.

There will be at least 4 checkrides before you can start working for an operator. You will need theoretical conversion course for the operator, CRM, Dangerous goods, first aid, fire fighting, ESE, Security & Heslo or part-SPO, part-M training for preflight and maintenance and possibly task training for maintenance related items depending on operator.

1. CPL skill test
2. Type rating skill test (You need type rating on each and every helicopter type in EASA).
3. Route/Role/Area & OPC conversion training and check (The operators checkride, probably similar to your part 135 checkride?).
4. Line training and line check

This is VFR single pilot only. There is more for multicrew & IFR.

Stay in the US. I would move to the US to fly helicopters in a heartbeat but not the other way around. More jobs, better pay, longterm career outlook and paths, no EASA to deal with, no age 60 rule and no flight duty time regulations... the list goes on and with many more reasons not to come to Europe to fly helicopters.

I think it's about time to build a wall between Europe and America to keep all these American immigrants from taking our jobs...
MAKE EUROPE GREAT AGAIN! :}

But only as a private pilot...

EASA paper Captains think Helo Ops are like airlines.