Sounds like a harmless flirt to me. Some Aussie blokes are like this - very informal, just being friendly, wanting friends more than anything else.
The way to handle it - sass him back. He's probably just as fascinated with your accent. You probably "made the mistake" of being friendly to him. I'd be curious as to how long he's been in the US.
I know you would consider yourselves to be a friendly, welcoming people, but it IS different, from what family and friends have told us. We also get visitors from the US coming here and commenting on how open Aussies are to each other. OUr Philly friends who stayed with us over Easter - we took them for a drive into the Southern Highlands, farming country (with the emphasis on COUNTRY). husband & I grew up mostly in the city (or outskirts) from farming stock, so we understand country folk. Not that there's much different to understand - only those completely absorbed into inner city life are likely to be nervous and insular. On our drive we saw a village fete and stopped to check it out (our friends were antique-hunting). As we walked around the various craft tables husband & I talked to various stallholders, chatted to other customers (as we're used to doing) and asked about the village. People chatted back, as they do here, it was very laid-back and friendly.
As we were leaving, a couple of other villagers were also heading homewards (in the usual leisurely pace of weekend village life) and called out "hooroo" to us.
My Philly friend turned to me and said, "So you've bumped into someone you know?"
I said, "No, she's just someone I was chatting to near the second-hand books."
Another bloke left, waved to us as we drove off. By this stage they knew where we were from, knew where our friends were from, had told us about their garden pests and the wife's pesky relatives, knew we were in search of antiques - but really didn't want to be nosy. They were just typical friendlies.
And that really is what we are like. It's typical, especially in country areas or even in city outskirts. As I said, only the most workaholic of central city dwellers/workers is insular.
People were amazed at how welcoming Sydneysiders were during World Youth Day - let me tell you, A lot of Sydney residents were NOT happy about it. That was Sydney, NOT being particularly welcoming. That was just us, being normal, not going to any trouble.
The Olympics 2000 - THAT was us being welcoming!
And Sydney is more insular than just about any other Aussie city except maybe Melbourne.
So depending on where your mate is from, and how long he's been there - I'd say you were friendly to him in a way that felt familiar. He's probably homesick. If your husband turned up at work one day, this bloke would shake him by the hand and congratulate him.
So think up some gentle "country boy" insults, maybe some Down Under comments and deliver them with a grin. If he objects, tell him you got advice from another Aussie on how to make him feel at home.
Marg