Okay so what I would to first is focus on what impacts the moon landing has had on society, and then work from there.
Here's what pops into my head:
-united america around a common goal (space race)
-national pride
-created a global stage for science and technology
-solidified america's position as world power
Then, you phrase those ideas as an answer to the prompt, and make sure your thesis hints at the larger significance of the paper. My english teacher tells us a thesis should answer three questions: What are we talking about, what is our position/interpretation, and most importantly, why does it matter.
Here's a structure for your thesis:
The moon landing was an unprecedented event in history, and the beginning of an age of scientific and technological exploration. The moon landing had an incredible impact on society, ...(insert what you settle on as impact here)
Hope I could help!