How likely is it that a Librarian who only speaks English would be able to find a job in Finland, with a Master's degree from a US university?

The librarians in Finnish public libraries must have the ability of speaking and understanding Finnish. In addition, there are usually quite many candidates for any free job, especially if the job is not a temporary one. The employment situation is not too good in public libraries, where economical cuts are regularly executed. However, there might be some special jobs in other than public libraries (university and special libraries), where Finnish is not necessarily needed and required, if one happens to have other special abilities needed. Finding that kind of library work requires a lot of work and luck and possibly a work permit would also be needed, if you are not an EU citizen. Probably you would need also a network of Finnish colleagues to get through the bureaucracy.

Without wanting to be pessimistic at all, I could answer with three words: "not quite likely", especially to anybody from outside the EU. But if you are able to visit Finland and stay here for a longer period, you should try your luck of course. In Helsinki there is a special Multilingual Library (supported by the ministry of education) inside the City public library and maybe it could be a good starting point for you?

Heikki Poroila