The US has plenty of landfill space,
The US in general might have a lot of space, but most counties don't have the money to truck their crap from the coast to the middle of Iowa. As a result, a lot of landfills are indeed filled up, and landfill space is a significant issue. Just ask densely populated areas like the San Francisco bay or Miami what they do with their inert landfill - it's expensive, and they're constantly looking to reduce what gets put into landfills. Not because it's green, but because it's getting to be very expensive.
Styrofoam is as close to inert as we can come up with. I'd happily live on top of a former Styrofoam dump.
Congratulations, you don't have to feed yourself from the land you live on. Not everyone is that lucky. It's also butt ugly to have styrofoam get into everything, and just stay there.
No, the reason that Styrofoam was originally considered bad - the reason we were supposed to stop using it - was that it was blown into foam with CFC's.
Yes, that was one of the original reasons. Now it's bad because it finds its way into the ocean, where it is ingested by all kinds of fish, birds and other critters and killing them off, because it just fills up their stomach. And considering how much we rely on a healthy ocean to feed a good chunk of the world's population, that's almost worse than the CFC issue. The fact that it is inert is a huge issue any place you try to have a healthy ecosystem, whether it is for farming, breeding or just generally we-like-nature purposes.
even though Styrofoam is a better insulator and requires much less energy to make and transport.
Citation needed. Air is actually a better insulator, and the reason why it's cheaper to have a little double-walled cardboard ring in cups.
Every time I hear someone complain about how dumb green or environmentally conscious people are, I find someone who has even less of a clue, has a huge axe to grind and is an asshole about it.