Captain America would probably be very reflective. He might see his past self as a reminder of his long journey and how much he has changed. He could try to offer some words of wisdom to his younger self.
Tanjiro's fate in the manga is that he ultimately passed away. This event was a significant part of the story's development and had a profound impact on the other characters and the overall plot.
Tanjiro's strength in the manga is significant. He acquires new powers and techniques, and overcomes numerous powerful foes with determination and strategy.