That is the best answer you can give?
"Um...because he is US champ."
I don't give a d@mn if he is US champ. He has a PR of 3:36.92, which is 17th of 18 in the field (he is 0.06 ahead of the 18th seed, the mighty Manuel Olmedo (who has a 3:37 this year to Centrowitz's 3:40). There is no denying that he is a VERY weak element in the field. Totally outclassed. He's racing 3:29-3:31 guys, which is like him racing a 3:44 guy. He didn't even crack the world top 100 performances in 1500 last year.
Stopwatch, boys. Stopwatch.
He is a complete scrub in this field. Period. If your only argument is that he won USATF, you are only proving my point. There are plenty of non-DL races he could run in Europe. Ask the dozens of faster runners who race them.
Now, who got this scrub into a the race when there are a dozen or more other runners could take it to him any time?