Canon 7 of the old American Bar Association's ABA Model Code of Professional Responsibility (adopted in 1969, and amended through August 1980), reads as follows:
Canon 7. A Lawyer Should Represent a Client Zealously Within the Bounds of the Law
Ethical Consideration 7-39 sums up the nature of this obligatory zealousness:
In the final analysis, proper functioning of the adversary system depends upon cooperation between lawyers and tribunals in utilizing procedures which will preserve the impartiality of tribunals and make their decisional processes prompt and just, without impinging upon the obligation of lawyers to represent their clients zealously within the framework of the law.
From this example, we may infer that zeal, in and of itself, is not necessarily excessive or unacceptable. An adjective that describes inappropriate devotion to an interest or cause more accurately than zealous, it seems to me, is overzealous. I agree with the gist of AmeliaBR's answer that a good descriptive adjective to use in a religious or quasi-religious context is fanatical. A somewhat vaguer adjective that writers often use to signify beyond-the-pale enthusiasm or ardor for a political idea or program (which may or may not involve patriotism) is extremist.
In my view, both jingoistic and chauvinistic are too closely associated with forms of patriotism gone wrong to qualify as "not relate[d] to one's country (or state)."