Jurgen Klinsmann's team have been handed a difficult draw, grouped with Germany, Portugal and Ghana for the upcoming finals in Brazil.
The showpiece event will also be Donovan's fourth World Cup, having helped the US qualify past the group stage on two of the three previous occasions.
"For me it's a very easy equation," Howard said of Donovan at the nation's training camp at Stanford University. "If Landon's (Donovan) on the field he's in our top one or two players.
"That's just my opinion, whether that means anything I don't know.
"But Landon's humble and I'm sure he feels that way but for me he's easily one of our best players and he strikes fear in opponents."
"This brings the best out of everyone because every day guys are fighting for a chance to play in a World Cup and you never know when you get that chance again," he said.
"So it's made it very challenging but I think a lot of fun. The beauty is the guys all get along very well and when we go on the field we compete and then afterwards we're in the hotel hanging out and we're friends again so it's been enjoyable."
