Thankfully flying internationally from the US is fairly simple...you merely check your luggage at the check-in desk where they check your passport and give you your boarding pass. Usually there is nothing separating you from domestic passengers until you actually board your flight, depending upon the airport. It is recommended that you get to the airport a little earlier. The security checks referred to are the TSA checks that all passengers go through-similar to the metal detector checks at all airports. Some airports are more efficient at these than others. As for your checked bag, it sounds like that will be something you will find out when you arrive to check it in. I'd imagine it will likely depend on which agent you get.