Bellingham posted many pictures on the trip to Los Angeles, two of which included Alexander-Arnold by his side.
At a Six Flags theme park, they were also seen together on a rollercoaster.
However, Alexander-Arnold, 25, was also seen signing a Real Madrid shirt over the vacation, according to a photo that went viral on social media.
He gave rise to concerns about his future at Liverpool after he was spotted writing on a young boy’s Los Blancos jersey.
Before Bellingham, 21, signed a contract with Real Madrid, Alexander-Arnold and Jordan Henderson made an effort to persuade him to sign with The Reds.
Bellingham and Alexander-Arnold had been best friends in the England camp during the Euros, having grown closer since then.
When Alexander-Arnold, a player for Liverpool, came under fire for his efforts in the midfield for England, Bellingham jumped to his defense.
“He can control the game so well defensively in that position, which makes it so easy for me,” he stated.