The pair were both fined £1,360 for the breach of pandemic rules, with England manager Gareth Southgate blasting them for their actions.
Southgate confirmed the two players had not been in contact with anyone else from the England squad after meeting with the girls which meant the game against Denmark meant for Tuesday September 8, will still be played.
Greenwood, who had a stellar season, scoring crucial goals for Manchester United, has now issued an apology, after deleting his Twitted account.
He used Manchester United’s official website to relay his apology, saying his actions while on international duty in Iceland, which led to him being dropped from the England squad, were “irresponsible”.
Writing on Tuesday morning, Greenwood said: “Having now had the chance to reflect on what’s happened, I can only apologise to everyone for the embarrassment I have caused.
“It was irresponsible of me to break the Covid-19 protocols which are in place to protect players, staff and the public. In particular, I want to apologise to Gareth Southgate, for letting him down, when he had shown great trust in me.
“Playing for England was one of the proudest moments in my life and I only have myself to blame for this huge mistake. I promise my family, the fans, Manchester United and England that this is a lesson I will learn from.”
It was Greenwood’s first call-up to the men’s senior side after he represented England previously at youth level.