It is not just the average case, it's the rule in the US. The same terminal will be fast for swipe and NFC transactions while being terribly slow for EMV.

I'm surprised nobody has mentioned caching. The terminals are likely slow either way, but they can cache the swipe and appear faster.

This is not possible via the chip which requires synchronous communication with the terminal.

I half-remember an article I read a long time ago about chip and pin cards that mentioned asynchronous communication with the mothership as a big win for the chip.

The example it brought up was that because the chip's identity could be verified through local communication with the chip, purchases could be logged at the terminal and synchronized at any point with the payment processor.

Is there something about the US payment processing market that makes that feature unattractive? Are businesses subsidizing more fraud protection than in other countries by making transactions synchronous and hiring more staff?

What do you mean cache the swipe? You can swipe and have a receipt in your hand before the chip cards tell you to remove your card. They are simply way slower. NFC is similarly speedy in comparison to the chips.