The US wields far to much power to be sanctioned by NATO, G20 and maybe even the UN.
The US accounts for 75%+ of NATO spending. Meaning, the US could hurt NATO far more than the other way around. And, for G20 the US’s gdp is so great that any sanction levied against the US would be met by retaliation that could crumble sectors of foreign nations economies.
Also, have sanctions been levied against nations that do this sort of thing in the past? France had the yellow best protests in which the French government used teargas and rubber bullets to attack the protesters. Remember since the US is a federation of states, most of the government responses to protesters have been levied by individual Governor’s and Mayors. Which makes it even less likely that they would sanction the nation in its entirety.
Lastly, we have over 40,000,000 people unemployed. For the sake of the American people, the best thing would be to not worsen the economic catastrophe facing the nation.