I broke the Matches into two categories: Tiger is involved, Tiger is not involved. In terms of the US it yielded these percentages(100,000 simulations):
Tiger Fourball: Win 51.6%, Tie 12.3%
Tiger Foursome: Win 55.6%, Tie 11.4%
Tiger Singles: Win 72.5%, Tie 0%
US Avg Fourball: Win 45.2%, Tie 13.1%
US Avg Foursome: Win 44.7%, Tie 13.9%
US Avg Singles: Win 53.3%, Tie 0%
Note that a singles match can tie after the Cup has been decided, but for the sake of this I just assumed a 0% tie percentage.
I think the odds on Tiger might be overstated a little bit, because if Greg Norman has half a brain(remember his captains picks were Scott and Ishikawa) he probably won’t be using the Yang, Scott, Ishikawa(the weak links on his team) against Tiger. It’s probably a small difference especially when you consider that it makes the US slightly more likely to win all the other matches if the International best is matched against Tiger.
So, Finally I took those percentages and ran them through the XLSsports President’s Cup simulator 1 million times:
Again, these are skewed at the tops and bottoms, because the match will be clinched at that point and there is about a 10% chance the rest of the singles matches can end at a tie at that point. The most likely score is still US 18.5-15.5.