Yes in the sense that it generally means they're playing well for us to get picked for their countries. (Or not as the case may be, England must have some pretty horrific centre backs if Jagielka was picked in the squad in the form he's in)
No though in the sense that football has become more global, and there are players playing in every country of the world playing in all leagues in the world. For all the crap FIFA, UEFA, the FA etc go on about player burn out and we play too many games so scrap FA Cup replays etc. Im pretty sure having players play friendlies in Australia, South America etc. early hours Thursday morning, then being expected to play for their club at 12.30 on Saturday isnt good for burnout is it? The clubs are the ones paying the wages, yet its conceivable that they cant prepare for a Saturday game after an international break, because their players are all over the world, reporting back at different times, coming back with knocks etc.
In the case of McCarthy, looking at it from an Ireland and Everton perspective, he never should have been called up the last 2 times. A hamstring is one of those injuries that needs rest, or it will reoccur. Some injuries a player can play through pain, but a hamstring is one of those that needs to be managed carefully and a player cant be rushed back. Koeman was completely right to question Ireland playing him in 2 full games last month, when he hadnt played any football in weeks with a hamstring injury. He made one sub appearance for us, aggravated the injury again, and still got called up by Ireland, who seem now to be trying to make a point.