>Generally it's much quicker for a country's nationals to enter a border than foreigners.
The UK is somewhat unusual in letting nationals of a number of countries, including the US, simply scan their passports at an electronic barrier and pass through without speaking to anyone, essentially the same as their own nationals; it usually just takes a few seconds. Many EU countries do this for EU and sometimes other European nationals, but rarely for the US.
The US is rather unusual in having their own nationals need to go through a non-trivial border control process, even with Global Entry. However, this is in part because many European countries have separate border control and customs processes, with border control before baggage reclaim, while the US tends to have them combined.