Campbell had been snubbed for 16 months after joining Portsmouth until Mac finally recalled him for last month's Euro qualifiers against Estonia and Russia.
Defender Campbell, 33, said: "I hoped the England situation would change and I would be picked - and I was.
"Some people think someone's playing well just because they're in a big team, or players should be picked just because they're at a high profile club.
"That's rubbish. There are players in top teams around the world who are not playing good football.
"You've got to look at the player, not the club. You can have 10 bad games a season in a big club and get away with it."