Fight those who do not believe in Allah, nor in the latter day, nor do they prohibit what Allah and His Apostle have prohibited, nor follow the religion of truth, out of those who have been given the Book, until they pay the tax in acknowledgment of superiority and they are in a state of subjection [Quran 9:29]
In the early days, Jizya was a tribute paid by nations which had fallen under Islamic rule, which was common practice in the old days. And it is to this that Quran is referring to. Later on, Jizya became an individual tax paid by non-Muslim citizens: males who could afford it, who did not pay the Zakah tax which was required of Muslims and who chose not to serve in the army.
There is no separation between religion and state in Islam. The US government, on the other hand, is a secular government. We can argue till the cows come home which system of governance is better, but that would get us no where. An Islamic state does acknowledge that its non-Muslim minority is not bound by divine laws as the Muslims are. Therefore, it would be unethical for a Muslim government to ask for charity dues from non-Muslims in whose religion it is not compulsory to give charity. Furthermore, it is immoral to ask a Buddhist, for example, who believes in non-violence to be drafted into the army. You must agree that if only Muslim citizens pay charity dues and serve in the army and non-Muslims don’t have to do anything, it would be unfair. Hence, non-Muslims (usually males who could afford) were asked to pay a poll tax instead, which by most historical accounts was one gold dinar maximum per year, as compared to the 2.5% of their entire worth that Muslims must pay each year. Even so, Caliph Omar on his deathbed left the following instruction: “I instruct you to be good to the Dhimmis [non-Muslims] for they are your responsibility. Do not tax them beyond their capacity. Ensure that they pay the Jizya without undue inconvenience…With regard to the people, I enjoin upon you to administer justice with an even hand. See that all the legitimate requirements of the people are met. Be concerned for their welfare. Ensure the safety of their person and property…Treat all the people as equal. Be a pillar of strength for those who are weak and oppressed. Those who are strong but do wrong, make them pay for their wrong-doings.” You can find the complete test of his message at this web site:
Furthermore, if any non-Muslim tribes agreed to serve in the military or agreed to pay the Zakaat (charity which Muslims pay) they were excluded from paying Jizya.