Question about a legal/illegal business. Sex Crimes, Sex Offenders

I would like to open a website which services are legal in Spain. The users will only be able to post ads from those locations (by selecting those locations when they place their ads). However the website can be visited from anywhere in the world and users can become members from anywhere in the world (even if they cannot post ads as their location is not accepted). The thing is I live in the USA and my web server and company that will run this website will be based in my country of origin :Spain. So all the money will be generated from there. Can I have legal trouble if I live in the USA and I am the owner of that website, even if my services are not available for US costumers?. Thank you for your help.