[zarzavat]

The US also has some quite byzantine rules. For example, let’s imagine I fly from Europe to Canada, with a 3 hour transit in US. I stay four months in Canada because I’m a UK citizen and Canada allows me to stay up to 180 days. I return to Europe using the same route via US.

If I did that I would have overstayed in the US. Because the US only allows a stay of 90 days under the Visa Waiver program, and even though I only spent a few hours in the US, the four months in Canada counts towards the 90 day limit. The US also doesn’t have airside transit like most countries.

The correct thing to do would have been to apply for a US transit visa so that I am not entering on VWP, or to route my flight so that it doesn’t transit in US.