I'm gonna post this again, as I looked through every past season and compared it to the actual countries that had clues in:
I compared my total countries visited for each season with Phil's total, and he includes USA MOST of the time, but not all. There's only a few discrepancies:
In S3, England and Scotland are counted separately, but that could be counted either way.
In S9, Phil says 9 countries, but there are clearly 10 visited, so I can only assume they didn't count the USA this season. Brazil, Russia, Germany, Italy, Greece, Oman, Australia, Thailand, Japan and the USA all have tasks in them.
In S15, Phil says 8 countries, but there are 9 visited, so again, the USA isn't counted. Japan, Vietnam, Cambodia, UAE, Netherlands, Sweden, Estonia, Czech Republic and USA all have tasks in them.
In S20, Phil says 9 countries, which would imply the exclusion of Austria or USA. I'm inclined to agree with Airlinesguy and say that this time, the USA was excluded.
So 2 or 3 times, Phil has excluded the USA, possible in the most recent season. I definitely don't think we can say for sure that the missing leg isn't in a new country.. (My money's on Slovakia!)
But then again, pre-race press releases usually mention the newest countries..