The US Customs and Border Patrol have announced a new cell phone or tablet app for pleasure boater for reporting their arrival into US. This app, CBP ROAM (Reporting Offsite Arrival - Remote), can be downloaded from Google Play Store or Apple App Store at no cost. One will need to set up an account at login.gov to create profiles about the travelers and conveyances. It can be used by all travelers coming into the US via private vessel no matter the nationality of the traveler or the vessel. Please see https://www.cbp.gov/travel/pleasure-boats-private-flyers/pleasure-boat-overview/roam. Also, an article on theboatgalley website has additional information: https://theboatgalley.com/us-check-in-via-roam-app/
For a complete review of check in requirements for both US and Canada, please see the revised article by Brad Somers, Rear Commodore (Ret), US and Canadian Boarder Reporting Requirements.