- if you're deemed to be on US soil, constitutional protections (4A) apply; can't be destroying "evidence" unless you're accused of a crime or found to have committed a crime
- if you're deemed _not_ yet on US soil, then how can you be charged with a crime under _US_ law?
Also, that constitutional protections are suspended within 100 miles of a land, sea, or air border.
https://www.congress.gov/crs-product/RS22497
Although obviously not all US laws apply and enforcement is a whole other kettle of fish.
an officer can't stop me on the street and demand to see the contents of my phone -- unless they can show "probable cause" that I was about to commit a crime (based on other evidence), or I'm already named as a suspect or POI in an investigation. So if they ask to see the contents of my phone and I delete it instead (it's a very small bag in this example, Lol) am I obstructing an investigation?
If the investigation was legit, then yes. You should just say no. If you give the phone over to them or delete data on it after they ask to see it, you are destroying evidence. Does not matter whether you are the target of the investigation or not, they think you have evidence, you deleted it.
Just say no to the police and then keep your trap shut. This is especially true for federal agents.