To be quite honest, I'm surprised we haven't seen anything like this yet. I mean, it's nowhere near as easy to get the materials for explosives as it was in the 60s - crazy to think you could just drive up to a quarry and buy some dynamite. But there's still plenty you can do with a few trips to hardware stores.
I have to wonder if their cards aren't being tracked, and they're too stupid to use prepaid or cash to buy what they need - and so the feds are able to bag them, with their purchasing history as grounds enough. Or maybe they're just fucking incompetent; I dunno.
If we're going to repeat the 60s, though, we absolutely -need- to have another house explosion. Seriously, it's hilarious - Weather had ONE guy who was working-class, and he made the bombs. The rest of those fucking yuppies just had orgies and sex and wrote pretentious pamphlets, sometimes stuffing the bombs in a bathroom here and there. The ONE time someone tried to make a bomb that wasn't the working-class guy, he fucking blew himself up to chunks and the house around him:
https://en.wikipedia.org/wiki/Greenwich_Village_townhouse_explosion