Allow me to refute our resident mutant's claim that he/she represents a benign group of Xmen. This mysterious killer has zero good intentions for humanity, and in fact intends on replacing them with her own kind. Homo Sapiens eliminated their less-evolved kin, and Mystique's final goal is no different.
Though we lizards may seem frightening, and indeed have our own share of blood on our claws, but that blood also includes the willing sacrifice of our own kind to build a better future, one where mankind and lizardfolk can live in peace. Prior to this unfortunate incident involving the President of this United States, there was little cause for concern regarding our presence among you, and now that you have become aware of our presence, it only increases the opportunity you have to share in our technological bounty, and join with us as we explore the countless worlds of the cosmos. Now, naturally, such vast benefits cannot come without cost, and since the destruction of our own world has left us planetless, there are certain territorial concessions we would need in order to begin our partnership. For instance, we require a significant warm land mass in order to propagate our species, and expand our fleet. There are vast tracks of unused and underused land in the continent of Africa that would fit our needs perfectly. Any humans living there would naturally fall under the jurisdiction of their new lizard governors, but rest assured that they would be treated humanely. We have read extensively from the book, "How to Serve Man" and found its ideas quite enlightening.
As for the US government, naturally we would make suitable reparations for this incident. Weregild will be paid to the families of those affected, and we could even offer replacement personnel for those lost during this time of trial, and it would naturally be up to you personally, how that payment will be dispersed.
But perhaps this does not sway your opinion. You need only ask, and I'm certain that I can come up with a creative resolution that will satisfy you. All that is required, is an endorsement, and then you will have nothing left to worry about.