[BytesAndGears]

It depends… do the states share a common set of laws and values? Do the benefits of one state profiting transfer in part to other states? Is there a course for grievances to be settled across state lines with reciprocal legal coverage guaranteed? Are living and working standards reasonably similar, allowing companies to fairly compete across state lines?

Those statements are generally not true across countries, but generally are true across states within a country. Things like working standards across countries mean that another country can employ slaves and have uncompetitive costs due to free labor, causing an unfair environment for those same companies forming in countries without slave labor. That is much less likely within the same country.

So it’s not necessarily the same to frame tariffs across states to be similar to tariffs on other countries. There are meaningful differences that make it harder to ensure similar standards across countries, which can make tariffs be meaningful. It helps to account for externalities inherent to lacking the protections mentioned in the first paragraph.