I'm traveling to the US mainland for the first time in my life in a few weeks.
I am not overly stressed about privacy, but I have read that US immigration can really overstep their boundaries. Are there any simple specific steps to take on my devices to protect my privace when going through US border control?
Remove my main accounts from my phone/tablet and use dummy accounts? Or just removing my biometrics?
Ultimately you shouldn't cross the US border carrying devices or encrypted data which you aren't prepared to unlock for DHS/CBP, unless you're willing to lose the hardware and/or be denied entry if/when you refuse to comply.
Device searches were happening hundreds of times each month circa 2009 (the most recent data i could find in a quick search) and presumably it has gotten worse since then.
In 2016 they began asking some visa applicants for social media usernames, and then expanded it to most applicants in 2019, and the new administration has continued that policy. I haven't found any numbers about how often they actually deny people entry for failing to disclose a social media account.
In 2017 they proposed adding the authority to also demand social media passwords but at least that doesn't appear to have been implemented.
Well, on my ESTA, they said the social medias disclosure is optional. Just a tool to help you confirm your intents visiting the US (or to be withheld against you as well) https://esta.cbp.dhs.gov/faq?lang=en&focusedTopic=Privacy%20and%20Security&answerToDisplay=How%20will%20CBP%20use%20my%20social%20media%20information%20collected%20through%20the%20additional%20question%20that%20was%20added%20to%20the%20ESTA%20application%20in%20December%202016%3F