The US government asks tourists wishing to visit the country, the usernames from the social media they own.
Do you want to get a tourist entry permit for the USA? In the new application you will find on the page Electronic System for Travel Authorization (ESTA) which is part of the program US Visa Waiver you will also need to fill in information about them social media you have at your disposal. The US Visa Waiver program is a US visa exemption program that allows 38 countries to visit the US for 90 visa-free days.
The addition to the social media form was first proposed by US Customs and Border Protection (CBP) in June 2016. The form specifically prompts you: “Please enter information related to your online presence” and a drop-down menu along with a text box allows applicants to select a social media service (eg Facebook, Twitter, Instagram etc) and type the name user they use in it.
No, they don't ask for a password. We don't think they need it anyway. However, according to the US CBP service, the goal of this change is to localization potential terrorist threats. The CBP wrote last June that the collection social media data will enhance the existing investigative process and provide greater clarity and transparency into potential illegal activity and connections.”
Naturally, the proposal to fill in social media has been critical and protesting, as it was logical. Many human rights groups and groups, including the American Civil Liberties Union, published an open letter last August in 2016 expressing their "serious concerns".
It seems that these protests were the reason that the choice Surrender of usernames is optional, but because the process for entering the US is confusing, it is likely that most visitors will fill out the card completely rather than risk additional intimidating questions from uniformed officers.