Final answer:
Nick's statements highlight the potential for surprising events in the Jazz Age, represented by Gatsby's personal, singular journey as captured through Nick's flawed narration.
Step-by-step explanation:
The significance of Nick's statements: "Anything can happen now that we've slid over this bridge" and "Even Gatsby could happen, without any particular wonder", suggests a sense of possibility and the unexpected characteristic of the Jazz Age. F. Scott Fitzgerald, through his most famous character Gatsby, shows that individual stories can be both unique and universal.
Nick Carraway, as the sole, flawed narrator, allows us to see Gatsby's life in its singularity, without the need for it to represent anything more than his own story, making those unfamiliar and unpredictable occurrences in life distinctly plausible.