. . Will it strive to protect US interests (especially with "foreign" accidents)?
I personally don't believe it. Of all the organizations, courts, lawyers, victims families NTSB is probably the most honest, competent and impartial body. By the way it's European, Canadian counterparts are equally good but you go outside of North Atlantic or Euro-Asian countries and political, cultural, even religious considerations start playing significant role in aircraft investigations. And my God! specially courts and 'experts' hired by some side are the furthest from any impartiality. Let's not forget you can come up with the most bizarre theory about the accident to deflect the blame and you will find an expert to testify on your behalf as some recent GA accident court cases showed. So called courts of law are the last place to seek truth in crashes but they are definitely a good place to seek millions $$.