Could a Eruv become invalid if the majority of Jews are Mechallel Shabbos(desecrating the Shabbos)while using it e.g. driving a car in the boundaries of the Eruv, carrying and using mobile phones etc?
It depends. Did the Eruv organizers rent a portion of all residences within the Eruv boundaries?
The Shulchan Aruch rules (cited below) that a Jew who desecrates Shabbos cannot mevatel (lit. cancel) owned home space to the Eruv users, but rather the Eruv users have to rent that Jew's property. If the Eruv organizers rented space in all homes inside the Eruv through the fire chief or another municipal authority figure, the actions of those who desecrate Shabbos should not make a difference. However, if the Eruv is only for Jewish homes, for example, an entirely Jewish courtyard or an entirely Jewish apartment building, and no renting of property was done, then the public Shabbos desecration would disqualify the Eruv.
It should be noted that this is not a question of the Eruv boundaries, walls, or strings being disqualified, but rather the partnership between Eruv users (usually through a communal two matzos) that gives significance to the Eruv walls and strings.
כ' שו"ע (או"ח שפה:ג) ישראל מומר לעבודת אלילים או לחלל שבתות בפרהסיא אפי' אינו מחללו אלא באיסור דרבנן הרי הוא כעכו"ם ואם אינו מחלל אלא בצינעה אפי' מחללו באיסור דאורייתא הרי הוא כישראל ומבטל רשות