If you want to read better previews of US side than I could write, check these ones out:
You don't need a reason to root for America. But here are 5 good reasons to hate Portugal.
Portugal is often credited as being the first global imperial power. Their Empire started in the mid-1400s with the conquest of Ceuta in present-day Morocco. From there, the Portugese Empire spread throughout Africa and Asia, gaining footholds in India and southeast Asia as part of the spice trade. What to take from this is that the Portuguese were an Empire that was also involved in spice trading. So basically the combination of this:
Incredibly the "end" of the Portuguese Empire didn't occur until either 1999 when they gave Macau to China or 2002 when they recognized the independence of East Timor.
4. Bad Debt
In 2008 Portugal's financial sector began to crumble and their national debt skyrocketed due to repeated bad investments by their largest banks. In 2008 their national debt was about 72% of their GDP, putting them right on average with the rest of Europe. By 2014, their national debt has skyrocketed to nearly 130% of their national debt. If the US hasn't bailed their economy out yet, we may be doing so quite soon if the trend continues.
Portugal was governed by socialists until the mid-1980s and their constitution was changed multiple times to accommodate the principles of socialism and communism. In the 1980s, the constitution was amended twice (1982 and 1989) to transition Portugal to a democratic system.
2. The Biggest Lie of Foreign Languages
This space was going to be used to talk about Portuguese central defender and super-douce Pepe, but his red card against Germany knocked him out of this game as well. Therefore, I had to come up with something else. If you ever took Spanish in school (middle school, high school, college, whenever) you were basically told that Spanish and Portuguese were very similar languages. Wrong. This is a lie to make you think that learning Spanish has additional benefits besides just knowing Spanish (which is pretty cool, but knowing Spanish is not the same as knowing Portuguese).
1. Christiano Ronaldo
In any conversation of the best player in the world right now, Ronaldo is either 1 or 1a in conjunction with Argentina's Lionel Messi. His skill with a ball on his foot doesn't make up for the fact that he is a perpetual whiner.