And then the next question, how does this affect consumer spending, what percent of purchases get the 3d secure message and change their mind instead of confirming the purchase?
Huh? Your conclusion does not follow. A large fraction of the interchange fee is kicked back to customers.
The size of the pie being so much bigger means the issuer’s tolerance for fraud is much larger, but it’s orthogonal to whether there’s actually more fraud. In practice credit cards fraud actually impacting customers is vanishingly rare at this point.
If you take a look at some of the more "expensive" cards, interchange is often higher than 2%, yet issuers often pay as much only on certain categories, and flat cashback cards usually pay 1.5% (2% is relatively rare).
Compare that difference to a total interchange of 0.3% in the EU.