As touched on above, PayPal can be used in the US for many things. However, PayPal has a policy whereby it can only be used to deposit (and withdraw) and gambling sites that are licensed by a national authority. So, UK casinos featuring UKGC licenses are fine, but French casinos listed out of Curacao are not. This is often why casino players in the US can use PayPal to buy goods with US dollars but not deposit at casinos with it.