Not many companies in the USA are accepting credits cards from other countries. And if they do it takes a lot of requirements in order to be accepted or approved. Anyone can tell where this can be done easily? or what other alternatives are in order to use a credit card? perhaps there is a project to solve this need?
I don't think any such restrictions are there to use credit cards in the USA. I'm from Asia, and I went to USA few times, and without any issues, I used my credit cards for purchasing online and even in shops as well. Only thing is you should inform your bank to enable your card to use in any particular country.
But what I know is in India some places they won't accept credit cards issued outside India to purchase Indian railway tickets and bus tickets online. But other purchases can be done without any issues.