I wrote an article for this book about Bris Milah, on the subject of 8 reasons for our having gratitude for this Mitzvah. This is the second part of this series of sharing this article here.
Another reason for gratitude is because Milah lifts us out of a status of being Arelim. Yirmiyahu referred to all gentiles as uncircumcised, ki khol hagoyim arelim (9:25). There, in being critical of Israel, Israelites are accused of being of uncircumcised heart: v’khol beis Yisrael Erlei Lev, their bad behavior causing them to be worthy of punishment (Radak). Thus the metaphorical (heart-)foreskin prevents us from getting close to God, when doing the wrong thing. Presumably when we do right, we can never be called or compared to “Arelim.”