I am from Brazil, so I don't know the specifics of Tunisia. From what I have read, his policies mostly focus on immigrants with criminal convictions. In his January 25 executive order, he cites Border security as being critically important to US national security. The order states that, "aliens who illegally enter the United States without inspection or admission present a significant threat to national security and public safety." The propose of the executive order is cited as being "to direct executive departments and agencies (agencies) to deploy all lawful means to secure the Nation's southern border, to prevent further illegal immigration into the United States, and to repatriate illegal aliens swiftly, consistently, and humanely." According to the executive order, you will only be detained if you are suspected of violating Federal or State law, including immigration law. The order also calls to expedite individuals' claims of eligibility to remain in the US and to expedite removal of those whose legal claims to remain has been rejected. So, according to this executive order, as long as you are already in the country legally and are obeying the law, you should be fine.
The now infamous executive order from January 27, calls for a complete suspension of entry of all refugees to the United States and blocks entry for citizens of Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen. The ban was supposed to last for 90 days and indefinitely for Syrian refugees. It also barred entry of US Greencard holders from those countries. On February 9, however, A federal appeals court ruled to suspend the executive order.
For undocumented immigrants who are covered under the DREAM Act, Trump has shown sympathy, calling them "incredible kids." However, his policies towards dreamers remain ambiguous. He has encouraged law enforcement and immigration officers to act more aggressively to arrest and deport undocumented immigrants living in the US, whether they have committed serious crimes or not. Because of this, immigration lawyers and advocacy groups suggest undocumented immigrants avoid enrolling in the Obama-era deferred-action program. They fear the new administration could use dreamer's personal information to arrest and deport them.
Currently, you should not have issues leaving and reentering the country, given that you continue to abide by US law. However, the future is ambiguous. Trump has shown that he will bar entry into the US for individuals with a valid visa or greencard. You should expect more random screening and stricter border agents.