I think what mathanxiety is saying is that she wouldn't experience the same level of racism from the press. And nobody takes the tabloids seriously over there, unlike here where people just quote the Mail or Express like its fact.
Yes. Of course there is racism in the US, but we don't have mainstream media outlets exploiting racist, misogynistic, and xenophobic attitudes targeting one individual on an almost daily basis. Even Fox News is moderate by UK tabloid standards. And in fact, US media coverage of Meghan has often acknowledged racism in the UK and how it has been expressed against her.
One other thing: there are active conversations in academia and in many corporate environments on what Sooverthemill referred to as "intrinsic" racism. This requires a deep dive into the issues and an acknowledgment that internalized white supremacy and structural racism are pervasive in our society and that working to eradicate these is uncomfortable and takes a lot of work. People who have been involved in this kind of work often try to follow a basic principle of never being silent in the face of racism and calling it out when they see it. These types of discussions have definitely made their way into mainstream media in the US, which means that the general public is more aware as well. Meghan may be comparing that level of awareness with her own experience in the UK. And she may be wondering why no one in the RF other than her husband has spoken out.