I am a US citizen traveling from San Francisco-Paris-Barcelona. Do I need an ESTA to return from Barcelona-San Francisco.
Thank you. .
Nope! ONLY non-US citizens need an ESTA.
In the future there will/may be a similar form to the ESTA called ETIAS for US citizens to enter Europe but it is not in place yet.
No, as a US citizen returning, you’ll just need to show your passport.