Kaillie Humphries is now, officially, an American. And just like that, the US medal hopes in bobsledding at the Beijing Olympics just got much stronger. The reigning world champion in both monobob and women’s bobsledding was sworn in as a citizen in San Diego on Thursday, ending her long saga to become an American and have the right to compete for the US at the Olympics. She does not yet have her passport, but that is likely to be little more than a formality. Without the passport, there was almost no chance the Canadian-born Humphries would have been allowed to slide at the Olympics. “Most st…