It's getting more and more common these days that whenever I talk to people about travel, the US is completely off their list. The TSA, NSA, NYPD, Bloods and Crips, the reasons go on. It used to be that Disney Land was one of the reasons to go to America. More and more people I speak to who would have gone now say "meh" to the idea.
As people in the United States wake up on a Sunday morning in their time zones, I guess it falls on me to say that this all depends on whom you talk to. I know lots of people who desire to visit the United States. The United States is still second only to France as the country most visited by tourists from other countries.[1] That's remarkable to me because France has land borders with several other countries, all countries with large populations, while the United States mostly has to be reached by transoceanic air travel.
The original post says, "I have heard that if I have been to some countries I might be refused to enter the US." What it does not say is, "I have checked the United States laws and have checked actual practice of what happens at the United States border, to see how that compares with border control in other countries." And then there are a couple of anecdotes in the few responses. This is basically not a high-quality submission for Hacker News, as it doesn't promote the thoughtful, informed discussion that should characterize our community here.
The typical set of Hacker News comments about the United States from people who have never been to the United States seems to mingle two points of view. On the one hand, the United States is criticized as an undesirable place that no one would want to live in or even visit, given a choice. On the other hand, the United States is criticized as an inhospitable place that doesn't give free, unrestricted entry to anyone who wants to work or visit or settle in the United States. (Criticisms of United States immigration policy on Hacker News mostly take the form of saying that the United States should let in more immigrants like, um, the people who participate on Hacker News.) A fable attributed to the Greek author Aesop[2] may explain how these seemingly contrary opinions of the United States can exist in the mind of the same person.
[1] http://www.smh.com.au/travel/travel-news/the-worlds-most-pop...
http://time.com/10296/most-popular-countries-to-visit-map/
https://en.wikipedia.org/wiki/World_Tourism_rankings
(Some sources disagree on the exact ranking, but every source I checked puts France first and puts the United States in the top five.)