Okay, I just watched "The Girl Who Loves Powerglide". It's not said so, but it seems to take place in New York City, based on the group meeting in Sparkplug's garage, which has a duplicate Teletraan I station. Furthermore, they seem to go from NYC to the volcano and back again with basically no problem. The Decepticons are said to have that flying platform in the North Atlantic. Powerglide programs it to crash on top of Decepticon HQ. This agrees with "Day of the Machines" that Decepticon HQ is in the Atlantic. Carly's able to drive from Autobot HQ to the dock to take a speedboat out to Decepticon HQ in "The Immobilizer". I can only conclude that Autobot HQ and Decepticon HQ are in pretty close proximity to New York City.