The best way to explain Brexit is to point out that the European Union had the right of free movement. That is the Union allowed someone from one member state the ability to move from one member state to another. So, if someone was a UK citizen, the could move to any other member state. In addition, they would retain the benefits of their home country (sort of).
The UK retiree who wanted to move to France, Spain, or some other EU member state could do so with a minimum level of BS. This is the same as someone who lived in Michigan could move to Florida or California.
Brexit removed Britain from the European Union, which took it out of the regime of free movement. In other words, it re-established the pre-EU membership border between the UK and the European Union member states. In terms of the US,(or another Federated State such as Canada or Australia) that would be the same as suddenly setting up a hard border between one state and the rest similar to what exists now between the US and Canada, or the US and Mexico.
What was once a "quick commute" has returned to being a wait to be processed at the border. And this wait also goes for goods and services. Imagine how it would be if a hard border with customs and immigration bureaucracy appeared between US states. You sort of have the idea if you traveled between the US and Canada after the Western Hemisphere Travel Initiative (WHTI), which was introduced in 2004 by the U.S. government to strengthen U.S. border security and standardize travel documentation. Now, one requires a passport to travel between the two nations.
The tyranny of "Brussels", which is silly. Especially if you consider that UKIP leader Nigel Farage was a member of the European Parliament. Additionally, one of the reason for the European Union "dictation" of laws was to make commerce flow easily by harmonising laws.
Sadly, I am European, not British, if I have to choose. And I will happily put up with any bureaucracy I have to to keep my European Citizenship. I would prefer the minimum level of bureaucracy, but that isn't my choice anymore.