There are multiple anime voice actors who are in unions, for example Troy Baker, the English voice of Naruto's Madara Uchiha as an example, but I think something even bigger is that getting a traditional actor to come and voice act is very, very expensive to begin with, and one of the biggest examples that comes to mind is Keanu Reeves for Cyberpunk 2077.

One of the biggest reasons that the launch of Cyberpunk 2077 went the way it did was found out to be because simply getting Keanu Reeves to be in the game, paying him and his portions of the game were a large portion of the budget, which ended up making the game run absolutely terrible on PS4 and XB1, but in general, even hiring the voice actors that are on cartoons is pretty expensive, as although someone like Tara Strong has been in dozens upon dozens of American kids' cartoons, there is no anime or Eastern animation in her filmography at all.

Speaking of voice actors however, there's three voice actors who are members of Hololive's English branch. Ouro Kronii, who is Dottovu; Nerissa Ravencroft, who is Caitlyn Myers; and lastly, Elizabeth Rose Bloodflame, who is Eileen Montgomery/EileMonty.

But aside from that, it just makes sense that anime can't get the top tier actors or even some of the most prolific VAs for American cartoons, because anime for many of those top tier actors is seen as weird, as well as not paying enough for many of them to see it as worth it. I'm just not sure the clique situation with current English voice acting for anime will be able to change without the studios either deciding to hire dual language VAs in Japan or actually putting good money in for better voice actors, as I do understand why many people say that English voice actors suck as a whole, even if I disagree.