It is very surprising that Moodle does not support a state/province field out of the box considering all of the largest countries of the world are composed of states or provinces.
In fact ALL of the following countries are composed of states or provinces or regions:
The United States of America, the United Mexican States (yes, that is the legal name of Mexico), Canada, Russian Federation, Federal Republic of Germany, Italy, India, Federative Republic of Brazil, China, Colombia, Afghanistan, Albania, Algeria, Argentina, Armenia, Australia, Austria, Azerbaijan, The Bahamas, Bahrain, Bangladesh, Barbados, Belarus, Belgium, Belize, Bermuda, Bolivia, Bosnia and Herzegovina, Bulgaria, Cambodia, Chad, Chili, Congo, Costa Rica, Croatia, Cuba, Democratic Republic of Congo, Denmark, Dominican Republic, Ecuador, Egypt, El Salvador, Finland, France, Greece, Guatemala, Honduras, Hungary, Iceland, Indonesia, Iraq, Ireland, Jamaica, Japan, Kenya, Kuwait, Madagascar, Malaysia, Morocco, Myanmar, Netherlands, New Zealand, Nicaragua, Niger, Nigeria, North Korea, Norway, Pakistan, Panama, Paraguay, Peru, Philippines, Poland, Portugal, Romania, Saudi Arabia, Senegal, Sierra Leone, Somalia, South Africa, South Korea, Spain, Sweden, Syria, Taiwan, Tajikistan, Tanzania, Thailand, Tunisia, Turkey, Turkmenistan, Ukraine, United Kingdom, Uruguay, Uzbekistan, Venezuela, Vietnam, Zambia and Zimbabwe.
And some countries REQUIRE a state or provinces for a valid address, such as the United States or Canada, where the states or provinces determine the city/town names, not the federal government. (The largest countries like the United States, Canada, Mexico, Russia, China, etc.. are all unions, and the states have broad domestic powers, which often includes naming towns, building & operating roads & schools, and have their own police force.) This means that while there can only be one Springfield in a state, there can be many Springfield's in the United States (in fact, there are 15 of them).
I would suggest that the state/ province field be made a standard field considering that over 100 countries in the world have either states, provinces or regions within them.