又普法，美国对申请来美的人员有道德品质（moral character）的要求的

在美国移民局公布的不得入境的十大类型人之一，就是有过卖淫嫖娼行为的人员：

The following are grounds for inadmissibility due to criminal reasons:

“any person coming to the United States to engage in prostitution, or any person who has engaged in prostitution within ten years of his or her application for a visa, adjustment of status, or entry into the United States, is inadmissible. This section also applies to those who have made a profit from prostitution”

申请来美人员应该在签证表上都回答过这个问题的。

链接on page 4:

https://www.uscis.gov/sites/default/files/document/foia/Inadmissibillity_and_Waivers.pdf