חתם סופר על התורה, כי תבוא מ״א
וראו כל עמי הארץ כי שם ה' נקרא עליך ויראו ממך אחז"ל אלו תפילין שבראש
Devarim 28:10 says that people will see that God's name is called upon you, and they shall fear you. Chaza"l says that the way the other nations will visibly see this is when you wear the head tefillin.
Practically speaking, what type of protection and fear actually occurs? An example (as crazy as this may sound):
I went to yeshiva elementary school in Washington Heights, a high-crime area in upper Manhattan in New York City. When I learned this verse in yeshiva many years ago, I figured, maybe there's something to this. I guess I was naive, but I was also scared and desparate for anything that would work. So, I wore my tefillin on the street. Well, guess what? That identified me as a Jew and, inevitably, I was mugged five times. Fortunately, they only took my money and not my tefillin, which are more precious to me than any money.
Seeing that this didn't work, I became skeptical of this concept that others would run away when they see you wearing tefillin.
So, practically, why doesn't this idea work? Why wouldn't others be scared of wearing the tefillin on my head?