America's UA is not situational and I think the term is being used incorrectly in this context. Manifest Destiny is merely boring and doesn't add anything particularly powerful to your game like Babylon's Ingenuity UA or Poland's Solidarity UA does. While you may not ever have to purchase land tiles, getting them cheaper is always nice. And +1 sight on land units is hardly a bad bonus, it's just a bit weak compared to other 'blanket' bonuses like Bushido or The Great Warpath.
Does having a comparatively weak UA make America a weak civ? Yes and no. Yes because there are other civs with much more versatile (less 'situational') abilities, and No because the UA is still inherently useful and there whether or not you take advantage of it. But the fact that weakness exists and greatness persists would probably make America a candidate for a buff or a change to their UA to make them just as competitive as the rest.
Civs on the same level of 'situational UA' would be Spain and Denmark. Those two civs could really do with a change, even if their UA suits them thematically the same way America's does. I can't figure out how to get the most out of either of them most of the time.
Is Egypt's UA situational? Of course it is, since it only applies to you when you're building a wonder. I don't think anyone will call Monument Builders a weak UA however. And if you pick Egypt, you are probably going to try and build lots of wonders anyway. America is no different, but their schtick is grabbing lots of cheap land that they can see more of. An appeal to the imperialist-minded player that wants to know the lay of the land. In this case I like to think that people are nitpicking at Manifest Destiny because they can't see it as being competitive with other more flexible UAs or UAs that are suited to their playing style. At the same time, I can agree with some of them but I can't agree that Manifest Destiny is a bad UA. Weak, but not bad.
Does having a comparatively weak UA make America a weak civ? Yes and no. Yes because there are other civs with much more versatile (less 'situational') abilities, and No because the UA is still inherently useful and there whether or not you take advantage of it. But the fact that weakness exists and greatness persists would probably make America a candidate for a buff or a change to their UA to make them just as competitive as the rest.
Civs on the same level of 'situational UA' would be Spain and Denmark. Those two civs could really do with a change, even if their UA suits them thematically the same way America's does. I can't figure out how to get the most out of either of them most of the time.
Is Egypt's UA situational? Of course it is, since it only applies to you when you're building a wonder. I don't think anyone will call Monument Builders a weak UA however. And if you pick Egypt, you are probably going to try and build lots of wonders anyway. America is no different, but their schtick is grabbing lots of cheap land that they can see more of. An appeal to the imperialist-minded player that wants to know the lay of the land. In this case I like to think that people are nitpicking at Manifest Destiny because they can't see it as being competitive with other more flexible UAs or UAs that are suited to their playing style. At the same time, I can agree with some of them but I can't agree that Manifest Destiny is a bad UA. Weak, but not bad.