I think these shouts that he should go to the euros have a bit of weight behind them (not that I think he will go but I think maybe he should). Now this is probably premature but I'm just using it as an example. Rashford is no where near as good as Ronaldo (when at the same age) and probably will never be good as Ronaldo (not that thats anything to be ashamed of tbh).
But lets just look at what happened with Ronaldo. He went to the 1994 world cup, didn't play a single game. But you hear Carlos Parriera and Mario Zagallo talking about how they just wanted him to gain experience. And that worked out tremendously for Ronaldo who went on to become one of the best players ever and also featured in the next 2 world cup finals, winning one of them scoring both goals.
Now, this is England, and they probably won't win and his confidence might be shattered because England are, lets face it, shit. But its interesting to think about.