Yes, but the person I was responding to found it relevant whether Americans are more likely to overstay in particular EU countries such as the ones on which the

Yes, but the person I was responding to found it relevant whether Americans are more likely to overstay in particular EU countries such as the ones on which the US imposes visa requirements. The only possible tracking (for short-term entries) is at the Schengen level, as you say; the US does not require visas from most Schengen nationals. But the US does require ESTA+VWP from them if they don't seek a visa, and this is basically analogous to ETIAS.