To supplement IdrisSeabright's reply, Cellbrite now says they can hack any smartphone, and is selling tools to do it for $30,000. This has not been confirmed, and it's likely that Apple will find a way to block it.
Regarding the question of FaceID and TouchID, Apple has address that also. If you press the side button 5 times quickly it will disable FaceID and TouchID until the phone is restarted. And remember that a passcode is required after restarting the phone.
Note that the TSA has not actually asked anyone for access to the contents of the phone, they have merely taken it away for a few minutes. Possibly to test it for explosives. But they aren't saying.
The bigger problem is ICE; they have authority within 150 miles of any border, whether you are crossing the border or not. And there aren't that many inhabited places in the US that are more than 150 miles from a border, because the coastline is considered a border. And they CAN demand access to the contents of your phone.
One more thing you can do. Sync all of your content to iCloud. Log out of iCloud when in a situation where you might feel vulnerable. That will remove the content from your phone, but keep it safe to be restored when you log back in.
Of course, your iPhone isn't your only problem. Essentially the government can get access to almost all of your "private" information whether it's on your phone or not, and Congress has recently extended and "enhanced" the law that allows them to do it. As Scott McNealy (founder of Sun Microsystems) said over 20 years ago, "You have zero privacy. Get over it."