Fury sort of addressed this in the Avengers when they were caught building weapons with the Tesseract. Here's the quote from IMDB:
Quote:
Bruce Banner: I'd like to know why SHIELD is using the Tesseract to build weapons of mass destruction.
Nick Fury: Because of him!
[points at Thor]
Thor: Me?
Nick Fury: Last year, Earth had a visit from another planet that had a grudge match that leveled a small town. We learned that only are we not alone, but we are hopelessly, hilariously outgunned.
Thor: My people want nothing but peace with your planet!
Nick Fury: But you're not the only ones out there, are you? And you're not the only threat. The world is filling up with people that can't be matched, that can't be controlled!
Steve Rogers: Like you control the cube?
|
I don't know about a space race. I think regular humans in the Marvel universe are more concerned about protecting themselves, than exploring the galaxy because the majority of alien visitors they get are trying to kill them.