Ancient Free & Accepted Masons V's Free & Accepted Masons

From 1751 to 1813, there were actually 2 Grand Lodges in England.  The difference in AF and AM vs F and AM states goes back to a disagreement between these 2 Grand Lodges in London at that time. One group was called the "Moderns", but was actually the older of the 2 English Grand Lodges.  The other group was called the "Ancients", which became the "Ancients" in AF and AM.

Due to this disagreement, the 2 groups broke into separate Grand Lodges.  The disagreement was later healed around 1880, but by that time, there were lodges and Grand Lodges all over the United States that were descended from one group or the other, and so each group kept their corresponding initials with which they were formed, (which is the reason for which there are small differences within different states' ritual wording and Grand Lodge By-Laws and procedures).

Most Grand Lodges in the U.S. recognize each other and treat each others members as valid Masons. Also, all of the U.S. Grand Lodges recognize (and are recognized by) the official Grand Lodges of England, Ireland, Scotland and the Grand Lodges in most of Europe, Asia, Africa, South America, Thailand, India, etc.

In actuality, it does not matter whether you join an AF & AM lodge or F & AM lodge in the United States.

In the U.S., every regular lodge is under the jurisdiction of its state Grand Lodge. Due to the fact that there is no Grand Lodge Headquarters for each state's separate Grand Lodge, each state's Grand Lodge is, therefore, its own "headquarters" within that state's jurisdiction. All Freemasons, both AF & AM (which means Ancient Free and Accepted Masons, as well as F & AM, which means Free and Accepted Masons, trace their allegorical history back to the building of Solomon's temple in the Holy Scriptures.

Freemasonry was exported to the British Colonies in North America in the 1730s—with both the "Ancients" (sometimes also referred to as "Ancients") and the "Moderns" (as well as the Grand Lodges of Ireland and Scotland) which chartered offspring ("daughter") lodges, and organized various Provincial Grand Lodges.

After the American Revolution, independent U.S. Grand Lodges formed within each state.

Can I end my membership if and when I want to?

Any Mason in good standing (whose annual dues are paid) may withdraw from membership at any time.

Is Free Masonry a political group?

No. 

In fact, politics and religion are discouraged from being mentioned in the lodge because to do so may negate its collective peace, harmony, and thus, its universality of spirit.

Is Free Masonry Anti-Christian or religion??

No.

Freemasonry encompasses and welcomes members from all religions.

Will I be expected to change my religion?

No. 

There are no specific religions mentioned in Masonic ceremonies nor in Masonic prayers. Freemasonry is not a church, a tabernacle, a mosque nor a synagogue, nor is it a substitute for any of them or for any religious observance. 
 
In the United States, most lodges use the Holy Bible, however, if you are of another religion, you may request that your sacred holy book (Torah, Veda, Koran, etc.) be placed beside the Bible during lodge meetings. Some lodges have several sacred books to accommodate the different religions of its members. 

Lodges whose members are wholly of a specific religion may choose to use their sacred books.