This song is super easy, and I think this sounds correct.
Hopefully you'll agree.
E B C#m A
I woke up today a song was swimmin in my head
and I hummed it to myself as i got out of bed
and on the way to take a shower it all just dawned on me
that a song like this just might go down in history
[ Tab from: http://www.guitartabs.cc/tabs/p/phantom_planet/anthem_tab.html ]
E E7 A Am E
I quickly ran back to get my guitar
C#m A B
a pen and some paper
cause this whole world needs an anthem
and I'm trying to put the words where they belong
yeah this whole world needs anthem
and I'm hopin everyone will sing along
That's pretty much it. Just keep repeating those changes.