Nations aren't a real unit to anyone except for rubes. The reasons interests and nations roughly correlate is because the individuals who make a nation's laws and direct its spending are more likely to be financially entangled with the people who those laws affect and the people to which that spending is directed.
They will also be financially entangled with elites in former colonies, and the operators of extractive industries in weak countries that depend on outside investments, and with everyone in the financial industry globally. They're also financially entangled with family members and friends.
The only people anti-monopoly legislation helps are people who are less connected and less influential. The only place it will be supported (by the well-connected and influential) is in countries who are trying to protect domestic industries. Once the protectionism (or the nationalized industries) are destroyed, then monopoly becomes ok in time to get control over entire sectors of the economy and raise prices to maximize profit extraction.
Any concern about whether the US is dominating the world or not is only practical. It's useless to sic the US against a country that is being protectionist or refuses to denationalize if the US doesn't have the strength to properly make the people who reside in those countries miserable enough to support the opposition.