The general US public may not be interested, but the interview had an impact in the US as it was commented by media personalities, talk show hosts, newspaper columnists (including former presidential speechwriters), and even politicians/Members of Congress. Even the White House spokesperson was asked about it, although the matter was not addressed directly in the response. So it affected IMHO the image of the Royal Family or even of the United Kingdom in the US.
You have to keep in mind that the United States is a republic where, for example, the constitution guarantees a republican form of government to all the states and both the states and the federal government are barred from granting titles of nobility or knighthoods. Public officers are also barred from accepting those titles from foreign countries and naturalized citizens must renounce them upon naturalization.
On top of that, American kids are raised from childhood in US schools with this idea that US independence (what is called the American Revolution in the USA) was a just rebellion against a tyrannical King (George III). The nuances of the causes of the revolution, which BTW are spelled out far more clearly in the Declaration of Independence, are normally not properly discussed in public schools, and there is even less discussion on whether King George was personally at fault for the grievances of the colonists or, if the blame actually lay constitutionally with the British Parliament and the King's ministers.
In any case, what I am trying to say is that all of the above, plus the American "ideology" of meritocracy and equal opportunity (or at least the illusion thereof) make many Americans naturally suspicious of royalty and monarchy, and inclined to believe the worst about royals (the Americans who thought otherwise, i.e. the Loyalists, basically left after the Revolution to settle in Canada, which is still a monarchy, or were assimilated in the US).
It doesn't take too much then for Meghan to sound "credible" to Americans when she says for example that the BRF is "racist". Actually, even more so in this case, because Americans also tend to overanalyze social relations from the perspective of race compared to people in other multi-racial countries.