As for the fall out not being reported in US news, it is Sunday night, and if they weren't involved, then they wouldn't have a leg up on this. Wait until Monday to pass judgement.
As for no American politicians or businessmen, it can be explained by sample size:
The USA might have their own internal money dirty money path. Or maybe the tax haven of choice is another country for the US. Maybe the IRS has specific rules for Panama?
That this one company has skew/bias in the origin of its clients does not surprise me at all.
If we had variety of leaks from different money fixers from different countries; say from the Bahamas, Cayman Islands, Guernsey, Singapore, UAE, Monaco, Lebanon, Puerto Rico, Belize; and no US scandal, I would be very surprised.
Apparently the US has some sort of treaty with Panama to prevent its use as an offshore tax haven for Americans.