There are unfortunately many online casinos and poker rooms which block US and Canadian residents. If a casino accepts bets from a US citizen, they might be either breaking US law or perhaps their own licensing agreements. These online casinos therefore don't accept gambling from US citizens or from other jurisdictions that are attempting to prohibit online gaming.
There are still, thankfully, the majority of casino's still accepting US players and Canadian players. Although they do accept bets, they still have limits of which states can actually play, so check out their list of approved US states before playing and your local legislator to see if it's ok to play.
