User blog comment:Sabilsadat/How Spider-Man and the X-Men "spiritually" may still exist in the Marvel Cinematic Universe/@comment-1895174-20141124174837

''According to some sources such as the Daily Bugle Tumblr Page, the events to Amazing Spider-Man 1 occur sometime early in 2013. So, suppose the events of The Avengers happen in early-mid 2012, Peter Parker was not yet Spider-Man so he couldn't help.''

Yeah, but you think he or any of the other characters in the movie would mention something about how their city was invaded by aliens who came out of a hole in the sky and were stopped by a team of superheroes six months earlier. Or there would still be signs of the battle (i.e. damaged buildings) all over the place.

As for heroes showing up in New York after the battle, that seems to be what the Defenders series are doing.