When I put an estate plan together, I always start out with a will questionnaire so that I have all of the information I need to determine what documents are needed and to draft those documents. One of the questions is the client's citizenship and place of birth. I've had quite a few clients ask why I have that on the questionnaire.
One of the big reasons that your planner needs to know your citizenship is to know what estate tax rules apply to you. I've posted about this issue before, but the basic concept is that the estate tax exemption is not always available to non-US citizens. Another reason is to know if an international will is appropriate and to know if foreign law may apply to certain portions of your estate and plan accordingly.
A basic reason is Minnesota law requires that, for any decedent either born in a foreign country or leaving heirs or devisees who reside in a foreign county, notice for any probate proceeding must be provided to the consul or other representative of that country. Giving proper notice is important, because it starts the window that creditors or possible heirs can bring claims. If proper notice isn't given, claims can be brought against the estate long after the family and personal representative thought the matter was closed. I include a reference in my wills regarding the client's citizenship and location of birth, if in a foreign country, in order to give the personal representive and their counsel a head's up so they can give correct notice.
If you have foreign citizenship or were born in a foreign country, be sure to let your estate planner know. Also, be sure to work with a planner who knows the consequences that your citizenship or place of birth will have on your estate plan.