I think I've had most of these in the past, but in my current campaigns, it tends to be more local threats.  Usually, either the good guys catch the bad guys, crime in progress, the bad guys come after the good guys, or the good guys are asked to intervene with the bad guys by some government agency.

So far in my current campaign, which started a few months ago, We've done the FORCE module, but the heroes weren't aware of the Nuclear threat until the end.  They are about to do the Destroyers and Dr. Apocolypse, so that will be the first time they've really been involved in a larger, Eastern Seaboard in danger, scenario.

I haven't ever really gone down to the street crime level, but I could see most of the scenarios coming up, and hope that as the characters level, we will get to them. 

Ours bounce all over the place (one might be international, the next street-level, the following intergalactic), but most take place within our own country (meaning usually somewhere in the U.S.).