Generally, there is no language requirement for accounting firms, but learning a second language is always a great way to open up doors in the accounting field. I have had friend and college who were able to take on international business opportunities because they knew other languages.
I would agree with everyone else that there is definitely not a requirement for a second language. That said, I have known a few people who have been able to use their knowledge in other languages to help out other teams and really stand out. For instance, if we have contracts that we need to read and understand that are in other languages, we will ask people who know that language to help translate the document so it is understandable for the rest of the team. I would say it's a valuable resource to have.
There is generally not a second language requirement for an accounting major. However, if you are studying at the undergraduate level, the business school or university may require a second language as a general education requirement.