China is an exception — flatbreads probably weren't eaten there.
Literal
Exception [topic-は] China [copula-で], probably flat breads [topic-は] were-not-eaten.
The conjunctive で (copula form) links the first clause (setting up China as the exception) to the second (explaining what made it an exception). 食される is the passive of 食する (formal 'to eat'), producing the impersonal 'was eaten.' おそらく ('probably, likely') is formal/written. Academic register.