Does a focus on strong national borders improve national security, or does it foster unnecessary fear of the 'other'?

A focus on having a strong border does not indicate fear of the "other." The US is (or was) a sovereign nation and having a border where we evaluate the safety of who is entering our country is not racist, it's protecting the people inside it. A good analogy is locking the door to my house. I don't lock it because I hate everyone outside of it, it's because I want to protect the people inside of it from the unlikely, although possible, chance that someone who wants to cause the people inside of my house harm; so that I have the chance to evaluate who is safe to let in and make that decision.