They don't want to get tangles in the US's bullshit, which is getting worse and worse the more time pass.
To be clear, I'm not saying that this is the reason, but it definitely is a reason.
In the case of Eushully, their way of thinking is seriously insular and circular af. They see the rest of us (aka, those of us who live outside of Japan) as a bunch of pirates and other unpleasant things. Some of us even approached them over the years (afaict, basically after Kamidori released) offering to help bring their games to various sections of the global audience, but they've consistently refused on grounds like the reason described above.
Some staff have even left Eushully and tried their own hand at global releases, like those who formed Animal Herb (Yano plus some other ex-Amayui staff), and did fairly well.
Compare that with a company like Alicesoft, another old guard, which has at least released some of their works on a global scale. Despite some troubles, they still do (Rance 03 came out recently, for example).
TL;DR: No, Eushully is just very old-fashioned in their way of thinking. While you may be right that U.S. bullshit is a contributing reason, it doesn't appear to be the core reason why.