That's an excellent point.
A US-made jet with Brazilian pilots, a Brazilian-made jet with US pilots, Brazilian controllers operating foreign-made systems - lots of potential for finger pointing even in the best of circumstances.
The best way to get an objective accident report with objective recommendations is to call on an objective third party. It won't make those closest to the event happy, but it can bring about a restoration of public confidence. (Which, judging from Brazilian traffic figures, is sorely needed.)
BTW, the impoundment of the Legacy should have given the opportunity for an outside electronics forensics expert to determine whether an intermittent wiring fault silenced the Comm and/or transponder. I hope the systems have not been disturbed to prevent this determination.