I beleive that Rashi in the begining of Parshas mishpotim states clearly that Mesira is ossur and a Chillul Hashem even in cases where the “arkous” (goyishe courts) have the exact same laws as Beis Din.
In addition I believe that there is a teshuva between Rav Elyashiv shlita and Rav Feivel Cohen shlita in which they both clearly state that from a halachic standpoint Hilchos Mesira are fully applicable in America.
However I would hesitate to think Mesirah applied in your case since the intent was simply to have the police have the person shut his alarm and not to administer an “oinesh” however please consult your LOR who is knowledgeable in this area of Halacha.