It actually goes deeper than just being a fan of football or soccer as we call it here in the US. Studies have been conducted as to why we (men mostly) fervently follow a team or club. Fact is, it's rooted deep in our DNA and dates back thousands of years to tribal and clan warfare. Certain tribes would dress a certain way or wear war paint in a certain manner. When we back a team, it's the same biological tendencies getting stoked; feeling of being attached or threatened by another tribe or clan. So we wear the colors, fly the flag, and some even paint their face. I must admit, I do get emotional when pulling for my teams especially those I have an emotional connection to like the Wisconsin Badgers (alma mater).
So, next time your woman asks why you get so worked up about a sporting event, tell her you can't help it it's in your DNA.
Because the US is out of the World Cup, I'm pulling for Poland and Iceland because of my ethnic hertiage.