I live 10,000km away from the US and can confirm that I get more spam on androids than when using iMessage. It wasn’t the main reason I switched back to iOS with my newest phone but it was a reason.
Maybe it depends on the Android vendor, but my OnePlus' "Messages" (the SMS app) automatically blocks a lot of spam messages automatically and it's quite good at it. On the contrary I have friends with iPhones who get spam/phishing messages.
Via SMS like everyone else with a mobile phone here, and especially around election dates. Apple’s done a few things recently to mitigate this and last election I reported a lot of phone numbers for spam to my carrier using a mechanism Apple built-in; so we’ll see if it starts to make a difference within a couple of years time.
