Bascially, it seems that "Judeo-Christian heritage" is an appropriate term because the founding fathers drew some of their inspiration from the Bible, and the Jewish faith is in step with the Old Testament. Plus, as some Biblical scholarly writings were in Hebrew, some of these were referenced in official and scholarly pursuits.
IMO, though, as we've discussed, the founding fathers were less religious than the prevailing trends (most were Unitarian or deist, and the US' founding documents certainly go out of their way to keep mention of religion to a minimum in the context of the period). Plus, the Enlightenment largely inspired our FF's, and a prime tenet of that movement was to separate religion from politics. Add the obvious Greco/Roman influences, and all the evidence still points to "Christian" or "Judeo-Christian" heritage only describing one facet of the country's foundation to the exclusion of the other - perhaps more important - influences.
