The Blues contingent - James, Ben Chilwell and Mason Mount - all arrived into the Three Lions camp on the same day as the Manchester City players they had beaten in the final in Porto a week earlier.
England boss Gareth Southgate had expressed concerns over what the final could do to the dynamic of the group, but the Chelsea full-back has insisted that he and his club team-mates have kept a low profile when it comes to talk of their success.
"I knew coming here that we just played against City, they're not going to be happy with the result," said James.
"We kind of had to be a bit humble with it we couldn't boast and rub it in. We just had to accept it.
“We know we won. Now we're here we’re together as a team with a massive tournament ahead and we need to fight together.
"The last few weeks have been very hectic, you know. We had a lot of games, massive games you know. We were fighting for the top four in the Premier League as well and we got that because we won the Champions League. Coming here you need to step away from club rivalry.
"We had Man City in the final but when we come here we're a collective team. We put it to one side. We're one team here and we need to work together."
Should he start at Wembley on Sunday, James could be facing another Chelsea teammate in Croatia's Matteo Kovacic - but the full-back is far from being concerned over the midfielder sharing secrets about his club mates within the England camp.
"I know how he plays as well so I’m sure I’m going to tell the lads what he likes to do and what he doesn’t like to do," said James.
"We’re coming up against a very strong side. They got to the World cup final and we know it’s going to be a tough game and we need to prepare right. Everyone needs to remain focused and give everything."