literal who?

• Minister to Spain during the Revolutionary War.
• A negotiator for the Treaty of Paris. Later negotiated "Jay's Treaty" which was deeply unpopular but arguably delayed another war with Britain until Madison got drunk on imperialism one night and started the War of 1812.
• Secretary of Foreign Affairs when the US was still under the Articles of Confederation (acting Secretary of State under Washington several months thereafter).
• Third co-author of The Federalist Papers with Hamilton and Madison.
• First Chief Justice of the US Supreme Court (albeit at this time the caseload was light, and the court's stature was nothing like it became under Marshall). This mainly included establishing how the court was actually supposed to do its job.
• Governor of New York for six years and got emancipation passed there.

Jay was incredibly influential in the early success of the US, but no one thing he did is individually "sexy", so he's not liable to be the focus of a secondary school US history lesson.

Washington, in particular, was an opponent of political parties as a whole, which he felt lent themselves to tribalism and graft.

Precisely because it was well-known that the First Amendment was meant seriously. As the Treaty of Tripoli says, signed by John Adams, one of the Founding Fathers who definitely was Christian, as ratified by the Senate:

As the Government of the United States of America is not in any sense founded on the Christian religion;

Effectively, secularism and pluralism were still, at that time period, radical 'liberal' ideas that many conservatives were not onboard with. I mean, shit, Jews were still kept in ghettos in most of Europe, and in most places only Catholicism or (generally a specific strain of) Protestantism were accepted, rarely both. Whoever heard of a country that wasn't founded on GOD!?