Americans are snapping, like crazy. And not only Americans, I know a lot of people from out of country are snapping as well, similarly to your Australian friend. The market is crazy hot. I'm not familiar with Cleveland, but I am familiar with Phoenix - the prices are up at least 20-30% from what they were a couple of years ago, and the trend is not changing.
However, these are not something "everyone" can buy. It is very hard to get these properties financed. I found it impossible (as mentioned, I bought in Phoenix). That means you have to pay cash. Not everyone has tens or hundreds of thousands of dollars in cash available for a real estate investment. For many Americans, 30-60K needed to buy a property in these markets is an amount they cannot afford to invest, even if they have it at hand.
Also, keep in mind that investing in rental property requires being able to support it - pay taxes and expenses even if it is not rented, pay to property managers, utility bills, gardeners and plumbers, insurance and property taxes - all these can amount to quite a lot. So its not just the initial investment.
Many times "advertised" rents are not the actual rents paid. If he indeed has it rented at $900 - then its good. But if he was told "hey, buy it and you'll be able to rent it out at $900" - wouldn't count on that. I know many foreigners who fell in these traps. Do your market research and see what the costs are at these neighborhoods. Keep in mind, that these are distressed neighborhoods, with a lot of foreclosed houses and a lot of unemployment. It is likely that there are houses empty as people are moving out being out of job. It may be tough to find a renter, and the renters you find may not be able to pay the rent.
But all that said - yes, those who can - are snapping.