Today is the Día de la Hispanidad (our sort of national day), and for that reason, there has been a military parade in Madrid, with the presence of some US soldiers (along with other NATO nationalities).
Unfortunately, I can't explain the political background of this issue (it is hilarious)
By the way, you can compare this year's ZP attitude towards the US flag above, with the picture at the bottom (2004), when he was not still President of the Government.
Anyway, I'm glad this year the US flag could march along with the other flags, with a respectful attitude from our authorities and a general applause from the crowd.