SIRT"I mean, the FBI & DOJ may say they have a warrant to “lawfully access” systems, but what happens if & when one of those systems turns out to be in the wrong jurisdiction and the local intelligence service happens to be large, loud and powerful enough to raise a meaningful objection?"
Given the typical attitude of US government agencies, they'll say "Tough luck, suck it up" and ignore any attempt under international law to stop such efforts. The US has a history of ignoring international courts when they're being 'inconvenient'.
But what would surely be a lot more noisy is if Russia, or, perhaps more likely, China, started doing something similar 'for the good of the Internet' - to machines in the US. I expect US politicians would absolutely lose their minds over that, just look at the kind of idiotic hysteria they're displaying over TikTok. Because when the US does it, it is altrusism, but if anyone we don't like does exactly the same thing it is surely insidious.
I might just be cynical.