us based credit ratings agencies ...

Question:

Who let these USA based credit ratings agencies become so powerful that when they issue a ratings downgrade the downgraded party's ability to raise capital is adversely affected by having to pay higher rates of interest, except the good old USA of course?

One would have thought these USA based credit ratings agencies' credibility was destroyed by giving AAA ratings to bundled up junk prior to the 2008 GFC.

Personally I'm getting quite sick of reading about these USA based credit ratings agencies persistently sticking their noses in Europe's business and downgrading European debt left, right and centre just about every day - and so worsening the serious plight in Euroland.

Why for example, are no USA states which are effectively broke being downgraded day after day after day etc etc?

Of far more relevance to me is what the Chinese based ratings agencies have been doing - including their USA based credit downgradings.