With the government seeming to want to wait for 11th hour politics to kick in on the debt negotiations, Standard and Poors rating services has threatened to lower their ratings for insurance carriers, securities brokers, mortgage bankers and other financial firms if Congress and the President don't agree on a plan in time.
So what if they do? Didn't they and other ratings services say AIG and other big wall street companies were solid until the day they crashed? Yes, they did. And yes there are still parts of the financial world that take into account the S&P's rating of a particular financial investment before they will buy it or grant credit.
My thought on this is that if the S&P, etal., lower the rating of these companies, including Fannie Mae and Freddie Mac, it will make it harder to get loans and credit. I don't think that it will have that much impact on world trade unless the the government does default, even if just for a few days. Many countries are in financial turmoil right now through out the world. There are other ratings methods and ratings companies as well as measures of how a company or a country is doing. We have to take the bad with the good and look at the whole picture.
As for property and casualty insurance carriers, California and many other states have fiscal solvency requirements for those carriers doing business in the state as admitted carriers. A company has to do more than be able to pay all its policies in the state. They have to have reserves over and above their operating costs. I don't look for your homeowners insurance carrier to be seriously affected by what the ratings services do.