as the title says how to get a United States with a parliamentary system what's the best chance here will be after independence or say the secession of the Confederacy but with severe repercussions with secession
Wrong forum. Multiple member electorates (3/5th). Almost as if historic. Have to break the weirds Lords system they developed indigenously. Also the districting of MmeMPs is problematic. Also they probably don't want to view themselves as 13 electorates.
Hmm, not the US per se, but Rhode Island could use a reform of its (17th/18th-century quasi-)parliamentary system of government. Either the Progressive Era or the New Deal period (as a continuation of the earlier swing towards Al Smith back in '28) could be ideal here. The main challenges here would not only be reducing political corruption, but also curbing the power of the Mafia so that it doesn't become the de facto fourth branch of government. Political reform would certainly be another feather to T.F. Green's cap.
Maybe George Washington kicks the bucket during the drafting of the Constitution and coalitions of factions become a necessity to get anything done. Also I second the calls saying this cannot be done with a post-1900 POD. Alternatively if Britain became a crowned republic rather than a system where the monarch had real but limited powers, then the new USA would be more likely to retain a parliamentary system, although this would have to be done in a manner that doesn't butterfly away the ARW.
Andrew Johnson tries to use executive power to completely stop and end Reconstruction.
Combine that with Grant wanting a easy job and not wanting to work hard, radical Republicans get enough support to amend the constitution and create a parliamentary system to strip the executive branch of its power.