The Bush League is a term for all associates of the Bush family, past and present, who have played a role in their ascedance to the throne of America.
It emphasizes the Texas origins, evidence uncertainty and unverifiable nature of some Bush associations and alliances, and also the apparent amateurishness and silly nicknaming (like "Brownie") that tends to make them appear less threatening than they are.
Ronald Reagan for instance is included, since he was elected thanks to Iran-Contra and had George H. W. Bush, the only Vice-President of the 20th century to be elected to succeed as President (somehow - hm)until Al Gore (who was magically not allowed to serve - hmm) in 2000.
Lee Harvey Oswald is sometimes included as a patsy for whatever went down on November 11, 1963, since he had much to do with Cuban exiles including some involved in the Bay of Pigs invasion that was (according to rumour and accounts that are reliable and do not contradict each other) planned and maybe executed, and certainly approved, by George H. W. Bush, but failed due to John F. Kennedy's lack of support for it after it had actually landed. It is also believed that Lyndon Johnson and John Connally may have been "in League" but this is more far-fetched as they were both Democrats.
Osama bin Laden is usually included for his key role with the CIA in Afghanistan in the 1980s and for the Binladin family (they changed the spelling to dissociate themselves) involvement with Carlyle and the way all members of this family were quickly spirited out of the country by George W. Bush on September 11, 2001. Also those who believe Bush Knew about 9/11 also believe there is some conspiracy or deal between Osama and Dubya.
Known, obvious and direct associates of Prescott Bush including Nazis are included, although Adolf Hitler himself is not believed to have met Pressy, the latter certainly worked for the former's war effort, continuing to ship clandestine war supplies to Hitler until the companies doing this were confiscated in 1943.
Also included are Saddam Hussein for allying strongly with the US due to the influence of Donald Rumsfeld and invading Kuwait with the tacit support of George H. W. Bush and Cheney, which backfired when Margaret Thatcher made them invade it and give Kuwait back to those pesky oil sheiks. For this, Thatcher doesn't make the list, although Tony Blair sure does.