Funny thing about credit ratings agencies: instead of warning there’s a bomb inside the building, they have a marked tendency to subsequently examine the rubble and announce it’s not worth as much as it used to be.

Standard and Poor’s and Moody’s were doing just that overnight, furiously downgrading sub-prime mortgage-backed securities long after the bomb they helped build went off.

The ratings agencies belatedly coming to their senses was only one of several hits suffered by Wall Street overnight. America’s biggest home builder is expecting a third quarter loss with new home orders down 40% while Home Depot and Sears both downgraded profit expectations as the housing shake-out flows through the retail system. It was enough to rattle US equity, money and currency markets and gave the ASX a shakey start this morning.

Yes, it is looking a bit more serious in the US — but it’s only the US. Ten, even five years ago, the current American problems would have been enough to seriously damage the international economy, but that’s no longer the case.

Our American-centric media will still beat up plenty of headlines about it, but the US now is only one of the world’s major economic drivers, instead of being the world’s major economic driver.

There are many Australian companies carrying large exposure to the US, but our economy overall remains a global rather than American citizen. Scaremongers will point to the risk of an American retail slowdown reducing China’s manufacturing exports and therefore China’s economy and therefore our exports — but China’s economy is broadening beyond the “consumer of last resort”. And it wouldn’t be such a bad thing if it grew a little less frantically anyway.

When the US sneezes, the world no longer catches a cold. It’s just that plenty of headline writers and the more panicky stock market traders don’t realise that yet.