Yes. Here is why:
If the police are at your door with a warrant, they have already shown sufficient probable cause to a judge to show that a search warrant is justified. Due process is being followed.
If the police are demanding your password, you as a citizen of the United States have a constitutional right under the 5th amendment, and under legal precedent (Doe v United States, 1988) to tell them to go fuck themselves:
The Foundational Doctrine: "Testimonial" vs. "Physical" Evidence
Under the Fifth Amendment, the government cannot compel a person to make an incriminating testimonial communication.
The Safe Combination Metaphor (Doe v. United States, 1988):
The Supreme Court drew a famous distinction regarding self-incrimination: Compelling a suspect to surrender the physical key to a lockbox is permissible because it is physical, non-testimonial evidence. Compelling a suspect to reveal the combination to a wall safe violates the Fifth Amendment because it forces the suspect to surrender the "contents of their own mind".
Application to Passwords: Most courts treat an alphanumeric passcode or PIN as the modern equivalent of a safe combination. Recalling and providing it requires cognitive effort and confirms knowledge, ownership, and control over the device and its contents.
Grabbing some dude's phone at the border under the guise of border control, when that dude is a US citizen and has shown documented proof; and then demanding his password to unlock it is a violation of his 5th Amendment rights. Moreover, there was no probable cause for the seizure of property, and without a court order for the retrieval of evidence (a search warrant) it remains his non-legally-encumbered property to do with as he pleases, including giving them the password that is a metaphorical string tied between the doorknob and a shotgun trigger.
There was no crime for them to investigate, and therefore no probable cause to issue the illegal search. There was no court order from a Constitutionally empowered judge to approve agents of the government trampling this man's rights.
HTH.