Nowadays, the political impact of the Americas Cup is virtually nil. Sailing is no longer the commercial sledge hammer it was in the 19th century when the Cup first started. Also, for years, this was a competition primarily between the US and Britain. Since the application, Britain correctly considered itself to be THE primary maritime nation, and it must have irked queen and country to constantly lose to the USA.
However, over the years, commercial interests which had been prohibited from participation in Americas Cup racing were allowed in, so we started seeing the boats as not national but more commercially branded, which reduced geopolitical impact greatly.
Finally, the fall of the 12 meter handicapping rule made the race, in some people's eyes, into more of a trailer pull or monster truck rally than a true test of sailing. Today, the America's Cup has declined in stature and is interesting as a sports and marketing event, but has very little political impact.