[@Prince of Seraphs]
See the thing I think is because of the number of problems that have been caused by extra terrestrial beings earth probably grew a tad bit more defensive. Lemme explain what I mean. Even though we have characters like superman or Martian manhunter, it is not uncommon for there to be some kind of invasion. Like the threat that brought the league together (gonna call them white martians cause I don't remember), or the thanagarians, many of the threats who appear on earth are also from offworld. 

I'd say earth doesn't push to interact, but are still wary of who comes by this point in time. Or are at least trying to set plans in motion to better monitor any and all alien activity that comes to earth. Some countries are more lenient than others. So I'd expect to see some aliens here and there because there are heroes and other species he associated with those heroes, but I'm not expected to see to many who aren't watched or haven't had to go through legal means to be allowed on earth. If that makes any sense...