Question

That’s a great joke! I laughed. You’re so funny! Why am I laughing? This guy couldn’t tell a joke to save his life. I can’t stand this I wonder how soon I can leave
How does the difference between the characters spoken words and internal thoughts affect the story

Answer 1

If this is an excerpt from a story, I wouldn’t be of much help. But from a layman's perspective, it seems like the character is attempting to please the failed humorist or he or she would have been frank. This in turn may have triggered a chain reaction, prompting the humorist to continue with his jokes which would have further affected the character. He or she is also giving the former a false sense of happiness and appreciation.
This passage may not affect the whole story in a remarkably discernible manner, but it definitely proves the character's penchant for politeness. And that may be be a deciding factor in his or her further decisions that ultimately define the plot of the story.