TTR: Destination ticket value changes in the America 1910 expansion
Which tickets were changed?

The following destination tickets received a decrease in value:  (Source: this post by Days of Wonder Forums user "Baron Von Schmidt original") 


Sault St. Marie to Oklahoma City: now 8 points
Los Angeles to Miami: now 19 points
Los Angeles to New York: now 20 points
Seattle to New York: now 20 points


Tickets Probably Over-valued

It appears that the minimum number of trains required to complete a destination ticket was the starting point for assigning each ticket a point value. The claim is made  (in this post by Days of Wonder Forums user "Caboose")  that Alan Moon (the game's designer) said the ticket values were not supposed to be the shortest route between two cities. Lacking the context that this may have been said in, I believe the intent was to put to rest worries that some ticket values were mistakes or misprints, rather than to deny all connection between tickets' values and their minimum lengths.  (This post by Caboose from several years earlier shows (s)he had previously believed the issue was due to a misprint.) 

Additionally, if the changes were to "fix" the tickets to match their minimum lengths, they didn't fix all of them. It's been pointed out  (in this post by Days of Wonder Forums user "DiscJet")  that the Los Angeles to Chicago ticket and the 1910 expansion's Las Vegas to Miami ticket are each worth more than their shortest length.

I conclude that Mr. Moon decided the four changed routes were somewhat over-valued, at least for the 1910 rules (if not in general).

Attribution Note: I got the idea to look through the Days of Wonder Forums from aramis' answer. I don't have access to my copy of Ticket to Ride and the 1910 expansion at the moment, so I can't verify the route lengths or values myself.