Final answer:
During his presidency, Barack Obama made significant changes to the US's foreign and national security policy, adopting a more selective engagement approach and stepping away from international agreements.
Step-by-step explanation:
During his presidency, Barack Obama made significant changes to the US's foreign and national security policy. He adopted a more selective engagement approach, opting to use military force and drone strikes in other countries only when necessary to combat terrorism. Obama's decision to step away from international agreements such as the Iran-Nuclear Deal and the Paris climate change accords also reflected a shift in the US's foreign policy direction. Overall, his actions showed a mix of liberal internationalist and neoconservative approaches to foreign policy.