Most major international transfer airports (e.g. Narita, Hong Kong, Schiphol, Changi, even Moscow) have nice air side connections that don't require entering immigration. Ya, they'll still security screen you, but it is much quicker than when initially broadening.

America is unique in requiring all passengers to go through immigration, but in that case they are usually going somewhere else in America anyways so it would be a port of entry. Sucks if you are transferring in Miami to go to South America, however.

And China is interesting in the other direction: certain cities in China allow multi-day "transit" without a Chinese visa, so long as your origin and eventual destination are two different countries. So, for example, you can fly into Shanghai from the US, spend a couple days there, then board a plane to Tokyo, and China considers it to be one long "transit" not requiring a visa.

Extended stay transfer visas on arrival are not uncommon. Moscow has this, as does Hong Kong for mainland citizens without entrance permits. So if you fly to Europe from Asia via Moscow and have an extended transfer Moscow, you can get a visa on arrival to see the city for a day or two, or if you are mainland Chinese and fly to Bali via Hong Kong, you can have a one day layover and see Hong Kong even without a Hong Kong visit permission.

You can add doha to that list, they often do security screens but not always... An hour has been hurried/comfortable connection time multiple times, even made 50 minutes a few times. YMMV.

Cheap flights from Eastern Canada to Asia often stop in the US, which is a huge pain.

Perhaps next time I want to visit Canada I'll go

Melbourne -> Seoul -> Mexico City -> Montreal

The previous time it was Melbourne -> LA -> Newark -> Montreal, flying home Vancouver -> LA -> Brisbane -> Melbourne.

On the other hand, a cheap flight from the USA to Asia can have an easy airside transfer in Canada.