Cattermole getting picked by an England manager means nothing of the sort. Well not according to me anyway, everyone's opinion varies. There is no standard definition. If international class in your world includes Geoff Thomas then Cattermole is international class. If international class means you shine at that level then he is nowhere near international class.
It feels like I've typed this about 20 times now.
No but your bit about how you perform at that level contradicts with your bit about it varying by country. You could be first name on the team sheet for a poor country and get roasted every time you play. Not international class. You could be a fringe player for a better country but hold your own whenever you play - international class.
Your latter point has baffled me. As for your former point, you say "shine," I say "hold your own." The question is, would Cattermole be able to hack it against decent (top 30) international teams if he was picked?