「」。
Baseball is often called 'America's Great Sport.'
Literal
Baseball [topic-は] 'America [gen-の] great sport' [as-として] often is-called-[passive-呼ばれる].
~として ('as, in the capacity of') marks a role or classification — here, 'as X' is what baseball is being called. 呼ばれる is the passive of 呼ぶ ('call'), common in titles, descriptions, and fame references. しばしば is a slightly formal/literary adverb for 'often, frequently.'