MOST READ: MasterCard, Visa Test Limits

"There is obviously going to be pressure on volume growth, but we do feel there are other levers to them to offset pain," such as expense cutbacks, says Sanjay Sakhrani, an analyst at Keefe Bruyette & Woods. He maintains outperform ratings on both stocks.

MasterCard derives roughly half of its revenue from its U.S. business, while about 59% of Visa's revenue comes from the U.S., Fox-Pitt's Shapiro estimates. He remains "comfortable" with his earnings estimates on Visa of 47 cents a share for the quarter, according to a separate note.

Last week, American Express posted second-quarter profit that fell nearly 40%, as even wealthy consumers have trouble paying their bills these days.

"The scope of the economic fallout was evident even among our longer term, superprime card members," Chairman and CEO Kenneth Chenault said in a company statement.

Discover Financial Services also recorded higher customer delinquencies when it reported earnings in June.

Several large banks, including Bank of America (BAC Quote), Washington Mutual (WM Quote) and Citigroup (C Quote), also acknowledged that customers were increasingly having trouble paying their credit card bills because of the weak economy and rising unemployment.

BofA, which captures the largest market share of credit, debit and prepaid cards, said "managed" credit card losses of 5.96% represented "more than 60% of total consumer losses" during the second quarter.

"We've continued to see increased delinquencies in our card portfolio in those states most affected by the housing problems, while other states have actually shown some declines. California, Florida, Nevada and Arizona make up a little more than a quarter of our domestic consumer card book but represent about a third of the losses," CFO Joe Price said last week.