I don't have hard numbers, but I can say that spam on both sides of the ocean exist. In the US, we get a lot of SMS spam targeted at homeowners, pestering them about selling their property, since there's a lot of open data about property ownership. In Germany, there's frequently spam pretending to be one of the major shipping companies (DHL for example) or the local customs office (Zoll) saying you have a package that couldn't be delivered and to click on a link. I've found the source for this data to be customer data leaks.

So yes, spam is a serious concern. WhatsApp spam exists as well, but since there's a central authority, unlike with SMS, it's a lot harder to avoid being shutdown.

I'm getting somewhat noticeable (once every few weeks) phishing attempts on Telegram and Instagram, less frequent on WhatsApp. On Instagram they sit unobtrusively in "requests" and disappear after some time, in Telegram and Whatsapp they do pop up and have to be deleted.

I think everyone's spam experience on the various platforms just tends to vary a lot. Some people see iMessage spam, while others swear they haven't ever gotten one. Ditto for all the other services.

I see SMS/MMS spam in spurts; I'll get one or two spam messages a day for a week or so, and then nothing for months. On Whatsapp, I get a few spam messages a month. I've never seen spam on GChat or FB Messenger. I don't use Viber or Telegram, so can't speak to those.

(from India). We have huge SMS spam. Significant spam for me ismarketing SMS from companies. They automatically sign your number up for example when you make a purchase/at POS. No opt-out - its eternal

We do have facility for DND with Deparatment of Telecom but seems to come up short as mine is in DND but receive several messages and calls through out the day.

I don’t see how it would make a difference anyway; iMessage will still display the regular SMS messages, so iMessage users are still susceptible to spam. (I checked and as an iMessage user I had about 10 in the last month)

Every couple of weeks I will be added to a spam Telegram group, maybe once a month I'll get a spam or scam whatsapp.

I have had the occasional iMessage spam too but haven't seen that in years.

On Android, I get dozens of spam political texts a day.

Luckily Google has added anti spam features to Google Messenger for years now and it filters out 99.999% of them. Once in a blue moon, a txt will slip by and i have to mark it as spam.