Complex sentence: U2 manager Paul McGuinness had long wanted to have the band filmed for a concert video, in order to demonstrate the band's potential and live prowess, and he wanted to showcase the band to American audiences not yet familiar with them.
Split into simpler sentences: U2 manager Paul McGuinness had long wanted to have the band filmed for a concert video, in order to demonstrate the band's potential and live prowess. McGuinness also wanted to showcase the band to American audiences that were not yet familiar with them.