I was held for two hours. The first round of questions was about my views on Hamas. Then the agents wished to know whether I thought Israel’s actions in the Gaza Strip amount to genocide and what I think of the slogan “Palestine should be free from the river to the sea”. I said yes, I do think Israel is committing genocide. As to the slogan, I said that in my view people anywhere in the world should be free.
Then the agents interrogated me about who I know in the Arab American and Muslim American community. They asked me to provide them with telephone numbers, took my phone away for quite a long period and asked to wait until they made some phone calls before they let me go.
AFAIK the basis for these checks were established under Bush. So mostly designed by Republicans and not democrats.