You just have to go with it, ride along with the story on its own retro terms... This is an old-fashioned, corn-fed, American hero with the straight-forward goodness and bravery that belongs on the front of a box of Wheaties. Thank goodness the filmmakers had the good sense to take him seriously - no nudges, winks, or cynicism - and make this adventure an honest period piece.
Captain America is, of course, copyrighted by Marvel Comics. I believe this is fair-use.
(Minor spoiler) At the very end, Captain America finds himself in present day Times Square... Frankly I'm looking forward to seeing him cope with modern America in the up-coming Avengers movie. Seeing the aw-shucks modest Captain America dealing with the Old-Norse bragging of Thor ought to be fun too. Now, even if Joss Whedon weren't directing that film, I'd be looking forward to it.