My understanding, from the last time I looked into this, is that the US does have decently aggressive laws against spamming people without offering them ways to opt out and some prior relationship, but a bunch of the spam originates in places outside the US and its immediate allies, so shutting it down becomes nontrivial.

I have, in fact, gotten periodic spam calls, though only once or twice an SMS - usually trying to solicit me about my car's insurance policy having issues (I do not own a car).

I sort of wish I could convince my Android phone to treat all calls to my direct number from anyone but GV as spam, because I have never given that number to anyone.