This is more of an economics question than a history one. The important thing to realize is that the US is the worlds largest advanced economy by a significant margins, and has been for a while. It is four times larger than the largest single economy in the EU (Germany) in population and output, and this relationship had been stable for 30 years. All in all, the US has been the largest consumer market on Earth for about 70 years.

There is a concept in economics called “increasing returns to scale”. It refers to a product or industry in which the marginal cost of producing one more unit is lower than the current one. It describes a situation in which the business that gains the largest market share quickest has the lowest costs. This generally arises in industries with huge fixed costs or large network effects. Credit cards are a classic example of a network effect industry (the card is more desirable to people based the more stores accept it, the more people who have cards the more stores want to accept it). So, generally speaking, credit card companies operating in the largest possible integrated market would grow strongest fastest. This is nothing to do with economic hegemony and everything to do with the fact quantity has a quality all its own.

Now this reality was complicated by currency fluctuations in Europe (the likeliest place for competing companies to arise) that hamstrung European finance in the late 70’s and 80’s. (Honestly, Europeans do not understand clearly enough how important the Euro has been at stabilizing their economies.) This meant that companies settling in greenbacks gained a stabilizing nudge during the ERM convulsions.

But overall, there is a tendency to characterize American dominance of certain industries to conspiratorial backroom deals. People do this simply because they don’t understand economics. The US was and continues to be the best place to start a firm engaging in an increasing returns industry, because it is still the biggest (in dollars) integrated consumer base.