Is a world primarily focused on intrigue and politics widely sustainable?

[aimlessPolymath]

Some observations:

-First, there are less "Default" enemies to fight unless a country is at war. One way to adapt would be to give other types of enemies elsewhere- criminals, maybe players can find some sort of equivalent to a privateer arrangement. If you opt to reduce combats significantly, you might want to shop around for systems a bit- D&D's noncombat rules are pretty anemic, and it's very much built around a paradigm of dungeons and "dungeons". For example, the mechanism of spells-per-day and "rests" (system-dependent) is designed for a particular scale of time pressure which may not exist in an intrigue game.

-Second, an environment in which a single group of adventurers can set off a war by accident puts players under a lot of pressure if they have to continuously worry about setting off a war- they might simply resolve the issue by not caring about it rather than considering all the ramifications involved. A game where you can't do anything for fear of setting off the much stronger powers-that-be is no fun. You might consider providing some cushion before a full-scale war erupts, and let them know about tensions as they rise so they have some time to back off or reconsider.

-Eliminating alignment is pretty easy to do- it either does nothing in some editions, or requires some minor class/spell tweaks in others.