They say that overall, 143 million people were affected.

There are about 250 million adults in the US.

I would take that to mean that if you're a US adult, with any sort of credit history, you're affected. The affected data for the larger 143 million was: "Most of the consumer information accessed includes names, Social Security numbers, birth dates, addresses, and in some instances, driver’s license numbers."

There's also a smaller set that had even more data exposed:

"In addition, credit card numbers for approximately 209,000 consumers and certain dispute documents, which included personal identifying information, for approximately 182,000 consumers were accessed."