No they don't all use the same data bases.

DNA Tribes supposedly has hundreds of populations, but they uses studies from CODIS markers, don't do them because CODIS markers are not for ancestry, they are for identity and paternity.

Not sure about Gedmatch, but it is free for a reason. If it were that good it would not be free.

Family Tree DNA,when they updated their admixture test from Population Finder to myOrigins, retrograded their reference populations,especially their non Europeans.

So that leaves 23andme and Ancestry.com. Not only do they have the Human Genome Diversity Project and 1000 Genomes but they also have their own databases (Ancestry.com has Sorenson)

For Europeans, 23andme currently has the most reference populations and samples. For African Americans, Ancestry.com is the best currently.

Federal law says nothing less than 72 years can be released.

The "72-Year Rule"
1940 poster
View larger image
Records from the 1940 census are still
protected by the "72-Year Rule." The
National Archives released them on
April 2, 2012.

The U.S. government will not release personally identifiable information about an individual to any other individual or agency until 72 years after it was collected for the decennial census. This "72-Year Rule" (92 Stat. 915; Public Law 95-416; October 5, 1978) restricts access to decennial census records to all but the individual named on the record or their legal heir.
For More information about the origin of the "72-Year Rule," see the following:

Letter from Census Bureau Dirctor, Roy V. Peel to Archivist of the United States, Wayne C. Grover, concerning the 72-year lapse between collection and release of decennial census records, August 26, 1952.
Letter from Archivist of the United States, Wayne C. Grover to Census Bureau Director Roy V. Peel, in reply to Peel's August 1952 letter (above), October 10, 1952.
Letter from Assistant Attorney General Robert G. Dixon, Jr., to General Counsel, General Services Administration, William G. Casselman II, Esg., concerning the origins of the "72-year Rule" and its evolution to 1973, June 14, 1973.

After 72 years, the records are released to the public by the National Archives and Records Administration. In accordance with the 72-Year Rule, the National Archives released the 1930 records in April 2002 and most recently, the 1940 records were released April 2, 2012.

Genealogy is NOT maths and it is NOT genetics

Clearly you are 100% American with lots of family stories, so genealogy is about proving and disproving those stories, that is all, it is about factual research of written records your ancestors generated during their lifetime to prove the person, then you can say you are an American of X ancestry