Unfortunately, there are some people in the USA that allow bigotry and prejudice to poison their thinking. It is all based upon fear. Since the terrorist attacks of 9-11, these people have developed a unwarrented fear of terrorism. They are willing to sacrafice some of our basic freedoms and principles in return for security. Their irrational fear of terrorism leads them to distrust anyone they suspect might be a terrorist. In their minds, they suspect anyone from the Middle East. They distrust anyone that looks like they may be from the Middle East. They distrust all Muslims.
Fortunately, the laws and the basic principles of the US government do not allow people to be judged simply on their nationality, their ethnic heritage or their religion. This forbidden practice is often called "racial profiling" or "ethnic profiling". Police and government officials are not permitted to single out suspects based only on their appearance, their ethnic background nor thair religion.
Unfortunately, not every police officer nor every govenment official practices what they are taught. A few government employees allow their personal prejudices to interfere with their duties. They do scrutinize and detain folks simply because of their appearance or their ethnic background.
One such case was recently highlighted in the news. An Iraqui refugee, living in the USA, was questioned and detained while riding on a train through Montana near the Canadian border. From all evidence, he was detained for over six days simply because he was from Iraq. The man was eventually released and he sought redress from the courts. He won. The US customs service issued a public apology to the man and he was awarded $250,000 in damages.
I wish I could offer assurances to every visitor that you will not be treated with disrespect nor delayed or detained, but I can not. I can assure you that the laws and principles of the US government prohibit any official from treating you differently simply because of your appearance, your ethnic background or your religion. I can also assure you that violations of these practices are rare.