The death of Hamas founder and leader Sheikh Ahmed Yassin could have serious implications for Americans. Up until now, Hamas, which has a lot of supporters in the United States, has deliberately avoided killing Americans. But now Hamas has announced that this policy will change (because they believe that the US "gave Israel permission" to kill Yassin). That exposes Americans to attack from another terrorist organization. While many Hamas supporters ducked for cover when the organization was declared a terrorist group in 1995, that hasn't stopped recruiting or fund raising in the United States. Hamas supporters overseas are now liable to be asked by Hamas to support terrorism in the USA. American supporters of Hamas support the terrorist attacks against Israelis. How many will support such attacks against fellow Americans? It only takes a few. But going to war with America makes Hamas more of a target for U.S. anti-terrorism forces. Israel says it is going after Hamas leaders wherever they are. American and Israeli intelligence agencies exchange information on terrorist operations and this could make Hamas leaders more liable to being located for Israeli killing squads.
Israel says it is going after the entire Hamas leadership. Until recently, Israel targeted the leaders of the suicide bombing operations, and the technical and support people needed to carry out these attacks. Hamas leaders were largely left alone so that there was someone to negotiate with. But now Israel feels that it's more useful to kill Hamas leaders than try to negotiate with them. Hamas has made it clear in the past that any negotiations would, at best, lead to a ceasefire, during which Hamas could build up its forces for further attacks on Israel. A recent suicide bombing attack at an Israeli port facility was interpreted as an attempt at really massive killings (by setting the bombs off near storage areas for dangerous chemicals.) For Israel, this was crossing a line, and it made the Hamas leadership targets.