It isn’t easy to excite Johnny Rzeznik these days. That happens when you lead a band such as the Goo Goo Dolls, which have multiple platinum-plus albums and an astonishing 17 Top Ten hits. But when the band was asked to headline Philadelphia’s ‘Welcome America’ show, which is slated for Sunday along the Parkway, the vocalist-guitarist was thrilled.“When I found out about that I said, ‘that’s awesome,” Rzeznik said. “I don’t think there is anything more American than playing on the Fourth of July.”Hopefully, the Goo Goo Dolls will get enough time to play a full set.The albums, much like the hit