I don't think so. In my opinion your premise is entirely incorrect. The EU was not in the business of severely harming a European-wide industry by developing the "class" RCD structure. Rather their intent in the whole affair was to construct a protective barrier around their boat building industry.
What you say makes no sense. The market for sailboats out of Europe it is pretty residual and European market is a huge open market. Many brands of all over the world sell the boats here, including American brands. The boats only have to be classified, as the Europeans ones, according with safety patterns regarding their use. That classification is not Political determined but technical determined.
If some political influence was made over the technicians was for those patterns to be less rigorous and not more
Europeans are by far the bigger builders of cruising monohulls and cruising multihulls, some groups produce both types of boats. It makes no sense to say that the multihulls or monohulls are discriminated in what regards safety standards and EC classification.
That safety classification has nothing to do with outside commercial protectionism but with citizens protectionism, with Europe being what Americans like to call, a nanny state.
Here a 30ft Cat builder cannot advertise his boat as an offshore boat without any kind of supervision. For that he would have to have a boat approved as a Class A boat and that does not happen with a 30ft Cat, not because the law does not permit a 30ft Cat as an offshore boat but because the boat will not be able to pass the requirements.
The EC mandatory classification says to citizens that a boat is built with the necessary scantlings and has the stability and the seaworthiness to pass a series of requirements that a large group of NA (after many months of work) determined as the minimum needed to be certified for a given wind and sea condition, monohulls and multihulls alike (even if the criteria is different). A 30ft multihull is normally a class B boat while some 30ft monohulls can make it to A class boat.
This has nothing to do with trade protectionism but with citizens protectionism regarding someone advertising a product that cannot safely provide what has been advertised, in this case a boat safe offshore.
Of course, all classifications are arbitrary in what regards to say if a boat is or not an offshore boat, but at least the EC classification his made taking into account the opinion of many experts in the subject (Naval Architects), namely the work made by many commissions on several European states and not an undifferentiated opinion.
The boat certification is a safety ,measure not different of the many safety certifications that are mandatory in the EC and has to do only with citizens information and protection. US has also some even in lesser extent that in the EC.