I’m not an expert at this, but is it true that the US is very unique in requiring interviews for all tourist visas and for almost every visa?

I’m American and every visa I’ve had to apply for did not require my physical presence at the embassy and I used a third-party processing service to get everything done.

Therefore, while I would need to apply to these countries from their US embassy because my physical presence was not required, I would generally not need to return to the United States to obtain their visa?

And this aspect of a US visa does make it significantly harder even though the application policy is similar to other countries?

I'm not aware of any other country besides the US that has a blanket policy of requiring at least one interview in almost all cases.

That said, back in the 2000s I had to apply in person at the French embassy for a student visa, in in the 2010s I had to apply in person at a Chilean consulate for a special visa.

Many countries have outsourced the bulk of their processing to contractors like VFS or TLS these days. But also, our experience as Americans is not representative as we generally have fewer visas we need to bother obtaining, and face less scrutiny when doing so.

I'm not sure if the US interview requirement makes it "harder" to get a US visa - it may be that getting a US visa is just harder than getting another country's visa, which might still be true even if we didn't interview people. The big thing that makes getting non-immigrant visas to the US difficult for many people is that, unless shown otherwise, US immigration law assumes you are an immigrant.