I'll answer that
האם נינג'ות בכל כפר מצייתות לארץ וללורדים המקומים שלה? All ninjas serve as the country's militaristic force, and they are under the direct control of the hokage. the hokage recieves orders from the feudal lord, as well as give orders. יכול להיות מצב שנינג'ה מקבלת פקודות סותרות מהוקאגה והלורד הפידואלי? there is no such case, since the hidden village recives most of his fundings from the feudal lond of the country. the hokage is also bound to follow orders from the lord, as mentioned above. כפר הצליל משרת איזו שהיא ארץ? The hidden village of sound is a village founded by orochimaru, he serves no counrty, even though, according to filling episodes, he IS part of one. האם נינג'ות הם שכירי חרב? Ninjas may serv as mercenaries if they either recieve such an order from the hokage, or, as in zabuza's case, freelance ninja. AKA renegade ninja. someone who betrayed his village authority. אכפת להם מלאילו מטרות שולחים אותם או מי צודק? Sunagakure (village of sand) is one example of villages who teaches how to not care for the assignments given to ninjas, but there ARE ninjas who care whether or not, their missions are justifyed, and what are the goals. but they're mainly pawns. יש בכלל לארצות צבאות או שכל הכוח שלהם מסתכם בנינג'ות? there is the feudal personal guard, but the entire militantic entity, of each country, is comprised out of the ninjas in their hidden villages. I hope I answered your questions ^_^
