US will play better in the second half.
The best futebol players are not the best because of their athleticism. Football is about skill more than any other team sport, and being a big guy is actually a disadvantage. Once guys get bigger than about 6'3" or 6'4" they're noticeably clumsy compared to the shorter guys.
As an example, look at Messi, Xavi, and Iniesta. Do you think they are great due to their athleticism? Do you realize there are tons of athletes all over the world who are big, strong, fast, and can jump high but couldn't make it as footballers even though they grew up playing the sport?
The US will get better when more of our kids play the sport in in a serious, dedicated way, and with better coaching. We're not going to win the World Cup with a bunch of buffed 6'6" guys on the field.