Following closely on the heels of heightened tensions between the United States and Iran, reports have surfaced of more than 60 Iranian-Americans being held for questioning when returning from Canada via Washington State. Most were released, some after up to 10 hours of questioning. Others were denied entry, at least temporarily.
Washington’s Lt. Governor Cyrus Habib said he received worrisome messages from friends that they or their family members were stopped and questioned at the Peace Arch border crossing at Blaine, Washington.
Details: News articles, https://www.nytimes.com/2020/01/05/us/politics/iranian-americans-border.html; https://www.newsweek.com/iranian-american-lt-governor-cbp-detained-iranian-americans-1481525
The Council on American-Islamic Relations (CAIR) has published know your rights material in many languages, including know your rights while traveling. The material is available at https://www.cair.com/KnowYourRights.