I don't get the connection. Amber alerts are when a child is missing. Yes, it can be a broad area. But the point is to be on the look-out for said child and/or abductor. They may have driven into your area.
Most of the amber alerts I've seen in this area mention that the child was last seen in a car, say,
for example a chartreuse Honda Accord, NJ Lic: ###-XXXX. (There are a few instances where an autistic child has wandered off, but they are luckily rarer.

)
I don't spend the majority of my time in the streets to scan different cars & licenses. I'm walking along the sidewalks of NYC or are down in the subways, trying to dodge pick-pockets, muggers and robbers. (A friend and I, last weekend, walked a wallet in to the nearby police precinct. It was just left on top of a pile of garbage, wide open with the owner's ID in plain sight. It even had an un-expired Visa card. The pickpocket apparently just took the money and dropped the wallet. We hope the owner was able to get back to NJ okay without his wallet.

) There is also an increasing number of
violent mentally-ill homeless people wandering around here to keep a general eye on.
I assume, (maybe inaccurately,) that some of the 20 people standing on the one street corner with me (x4 corners) are keeping an active eye out for amber alerts.
I don't have kids or are around kids a lot. I have an easier time telling the difference between a labrador and a golden retriever than being able to identify one child.

Now, if it was an
adult with a child acting weirdly, pulling a kid who clearly didn't want to go, verbally or physically threatening or hurting a kid who looked scared for their life, that would draw my attention & ring alarm bells. I'd immediately have my phone out, surreptitiously videoing them and then calling the police.