After 17 years of featuring American Express, Costco on Monday officially began accepting only Visa and debit cards. With millions of Americans impacted by the change, Jim Cramer dug deeper to find out how to make a profit for portfolios nationwide.

"This is the kind of investable story that is easy to notice in your everyday life. But that doesn't mean you should immediately buy Visa and sell American Express the moment you get home from Costco," the "Mad Money" host said.

Costco generated $116 billion in revenue in 2015, with much of that coming from credit cards. Additionally, over $10.5 billion in receivables from Costco's AmEx cards has now been acquired by Citigroup.

The stock of American Express fell 6.4 percent the day Costco announced the separation in February 2015. Since that time, it has continued to trend lower, down to $62 from $86 the day the news broke.

It is estimated that American Express lost 7 million member accounts, and as much as $76 billion in Costco related billings last year, $12 billion in related loans and a major potential international expansion.

AmEx has also suffered the same headwinds as all other financial institutions, hit by lower interest rates and increased competition from online lenders. It also lost relationships with Fidelity and Jet Blue.

On the flipside, Visa's stock has rallied 14 percent since the news that it would receive Costco's business in March 2015. The stock has been climbing ever since. Additionally, Visa runs the world's No. 1 largest payments network, but unlike AmEx, it doesn't lend money. Profits come from taking a small cut from every transaction made with its cards.

Cramer interpreted that as meaning that Visa is the exact kind of financial that money managers would buy safely in a low interest rate environment.

One would think that Visa stands to benefit the most in this scenario—but maybe not.

"I think this switchover is actually a bigger win for Costco than it is for Visa," Cramer said.

The deal is expected to save Costco up to $220 million, due to lower interchange fees. Additionally, Costco's new Visa rewards cards give customers a better deal than the old AmEx cards, which could prompt them to shop at Costco more frequently.

And perhaps more important, Cramer found that switching to Visa from American Express could dramatically expand the potential shoppers. With a much larger user base, Visa could potentially open the door to millions of new customers.

"Still, I think both Visa and Costco are buys here. My charitable trust owns them both, and even American Express with some changes at the top could regain the luster it lost not all that long ago," Cramer said.

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