Evenn though its onelayer down - the same tactics that were used to suspend/takeover domains would still apply , at the end of the day one still has to get the IPv4/IPv6 address from someone(who can be coerced).
When Trump pressures RIPE NCC or APNIC to deregister an IP address block, that's the end of the internet as we know it, and the return to national networks with very limited interconnection. Even Russia still has address registrations despite being sanctioned.
Alternatively they pressure USA ISPs to block the addresses. That's already regularly done but it probably won't be enough to satisfy the extortion industrial complex which is out for blood.
A quick look at the last few administrations is all anyone needs to see how this one interprets the powers and duties that come with the office.
One of my favorite phrases coined during the last Trump administration was something like, "not just wrong, but wrong beyond normal parameters." It basically meant exactly what we are discussing here; namely, being an outlier of some sort.
I specifically mentioned foreign policy. There, I don't remember a single US government that was not a net negative for the rest of the world (Israel excluded).
https://news.ycombinator.com/item?id=44379034