Although I found the game rather infuriating and/or not entertaining, it's nice to see some actual thought going into the concept of a game. The concept of wanting to go back and reverse time is particularly poignant in this context. The world indeed changed after the detonation of Fat Man and Little Boy; the US Empire's fate was sealed.
The last level of Braid did a fair job of turning game mechanics into narrative, which is a lot more satisfying than having a game ask you read big blocks of intentionally obfuscated text, so why is Braid 90% a game that asks you read big blocks of intentionally obfuscated text?