Off contract in June, Alexander-Arnold is said to have agreed to join Real Madrid this summer.
Souness, who 40 years ago left Anfield for Sampdoria, told the Mirror: “It was different for me. I was 31 and was leaving Liverpool having won a lot of trophies.
“I got a chance to what was, back then, the most lucrative league in the world. Italy was where all the best players were.
"For Trent it’s a different story. He’s 26 and he’s leaving his boyhood club. But he will come back a better-educated, more-rounded human being than what he is now.
“Going to another country, learning their culture, and seeing how they do things is good for you.
"I can’t be critical of him. He’s been at Liverpool since he was six, so he’s been a fabulous servant to the club he supports - and I think he’ll be a fantastic acquisition for Real Madrid.
“In golf terms, he’s got every club in the bag. He can pick a pass from 50 or 60 yards - and they will love him in Madrid."