Do you only send and receive emails with people in the EU?
If you advertise foolproof safes, but they end up not in fact being exactly that very thing you advertised then I'm sure you will have a great reason as to why actually your 'foolproof' safe can not be foolproof and you never guaranteed such a thing in your tos.
But at the end of the day, you promised foolproof safes, and you did not deliver.
Your argument is "well if you leave the lock open then...". And the reply to that argument is that "yes, we all know". The fact that I the user can make a mistake, does not excuse the company from saying "well, anyway, he would have made a mistake anyway so why bother"
As of now there's no guarantee of... anything, really.
Obviously if you decide to send an email to the US you're choosing to send your data there, that's a strawman.
In the moment that would be the Trump Administration for example.