This is what I was disagreeing with earlier - the assumption that TAA is either a 'bad' defender or that he's an average nothing-burger of a player somehow infused with Klopp magic that makes him good.
A lot of TAA's 'mistakes' come from executing the role Klopp has asked him to execute. Accepting positional risks in order to push forward. He makes up for that with good recovery speed but it's still risky. And he is now thoroughly used to that system. He doesn't play week in and week out as a pure defender, so dropping him into an England team where he is a defender first and wingback second will result in a drop in perceived performance. Had spent most of his career thus far as a more conventional right back, he'd be more comfortable and effective in that role. With all that being said, I am not denying that there are weaknesses in his defensive game. He can get caught out of position on set plays and during opposition buildup moves, and his attack-mindedness can detract from his ability to read the game when he needs to be defending. But if you really watch Liverpool play, you will see him do a lot of good defensive work every week. His role, however, carries with it the risk of high- profile 'errors' when Liverpool concede.
It's also fair to point out that he's 23 - some years off peak age for a defender yet, and substantially younger than some of the other right backs he's been compared to - such as Kyle Walker, who has a LOT more match experience under his belt. This, just as much as any issues of form or skill, is a valid reason to prefer Walker in the England setup.
I don't think it's a fruitful debate anyway. England have depth at right back and don't need him - if Southgate feels he's not the best fit I won't disagree and he has cogent reasons given his preferred style; Liverpool have won a league title and champions league with him as a major contributor. He is a specialized type of player but he is unquestionably effective at an elite level. He's just not (at the elite level) an all-rounder like James Milner who might not be the best at anything (except PKs, where he is ice) but are good at almost everything.
