Seasoned traveller as I am living in the US, the trick is to never transfer in the US on incoming flights. Outgoing is fine, because then they don't care. So when I go to Europe from LA I'm happy to transfer in the US if need be, but the incoming transfer has to take place outside, or else your looking at a 3-4hr PITA rigmarole. If you have anything less than 2hrs in between flights on a incoming US connection, you're probably not going to make it.