To legally operate in the U.S., you need to register for an online gaming license (just like offline casinos do). Licensed gaming sites display a special graphic on their site with their license number, are subject to auditing and compliance (just like offline), and pay taxes on their revenue. Consumers have an organization to complain to for any irregularities. Non-licensed gambling sites will be illegal in the U.S.
This may also alleviate the fears of many credit card processors- as far as I know, most will not work with online gambling sites.