The high rate of convictions for US Attorneys vis a vis state and local prosecutors stems from the higher level of prosecutorial discretion they enjoy. Basically US Attorneys only prosecute slam dunks. From the same source, you'll not that Florida for instance only has a 59% conviction rate.
Is that a sign of innocent people pleading guilty or a sign of an efficient judicial system? Got any stats to back up your inference that there are significant amounts of innocent people just pleading guilty? I'm not really sure what the point of your post was, but I don't have the ability to vote it down as irrelevant.