I am spending 10 days in the US and 10 days in Canada this summer, flying from the UK. When filling out the ESPA form, it asks if I am in the US 'in transit ' to another country- if I say no, I fill in details of my address while there for 10 days, if I say Yes, then no details are given. Which do I do?? It seems to make sense to fill in more info to allow them to contact me if required than not, but technically I am in transit- aren't I?
Nope, transit generally means you're just in the airport - continuing on to another place, so you won't be at any address within the US.
That's why if you say yes, you don't need to give details of an address, because you're not leaving the airport, you're just 'on your way'.
You're actually visiting the US though, before visiting Canada, and as such, you'll have addresses there that you can and should complete.