Westlife has not managed success in America , although their debut single , `` Swear It Again '' was a minor hit on mainstream radio and MTV . Despite their success in some parts of the world , Westlife have been unable to break into the US market . Their debut single and music video `` Swear It Again '' , released in the US in 2000 , was a hit on mainstream radio and the band even made an appearance on MTV 's Total Request Live .