In fairness though Mayo, Pikes Peak isn't a pass. There are quite a few Unipuertos that can be MTFs that are steep in the US, but a lot of the big passes tend to be the tempo grinder ones - and even when they are decently steep, they tend to be more consistent as they were made with more advanced technological equipment than a lot of the older passes like the main Alpine through routes or the central Pyrenees. Interestingly the eastern Pyrenees tend to be more along similar lines, and that possibly helps explain Tejay van Garderen's success in the Volta a Catalunya relative to other short stage races in Europe. The Tour of Utah includes probably the best mix of climbs in any of the US stage races as in addition to long but gradual passes it also has some climbs which are gradual from one side but steep from the other, and in its MTFs it sometimes even has roads steep enough for Sepp Kuss.
There are quite a lot of real HC types if you go for climbs that would have to be MTFs - as well as Pikes Peak (31km @ 6,6%) you have the likes of Mount Baldy (if climbed all the way, not the climbing part of a different side, then descending part of the toughest side, then climbing the same part of a different side then doing the last bit to the finish like the Tour of California did) which is 21km @ 7% albeit with the steepest stuff at the end, and a bunch of the climbs in eastern California a bit too far away from population centres for the race to have bothered with, such as Onion Valley Road (21km, 7,5%), Whitney Portal (19km, 7,4%) and from Wofford Heights east of Bakersfield you've got Alta Sierra Ski Resort (16km, 7,8%), although I suspect the Tour of California would have gone over Greenhorn Summit (the pass below it) from the much more gradual western side. As for steeper PASSES there's only really Palomar Mountain (20km @ 6,9%) and Gibraltar Road that really stand out as HC types that are that for steepness rather than length there, even if lots of other climbs are debatably or certainly genuine HC. Sure, there are plenty of more 'normal' HCs that are MTF only too (Horseshoe Meadows, 31km @ 6%, or Wolverton Ski Area, 33km @ 5,5%, stand out here as tougher examples), but that's typical in Europe too, there are plenty of big climbs that only average tempo grinder levels that are used as summits in Europe too, such as La Toussuire, Val Thorens, Arcalis, Cervinia, traditional Sierra Nevada, or most of the Catalan climbs like Vallter2000, Pla de Beret or Port-Ainé.
Elsewhere in the States you have e.g. Mount Washington (12km @ 11%, an absolute monster), Mount Equinox (8,4km @ 11,7%), Powder Mountain Resort (11,5km @ 9,7%), but most of the toughest passes tend to be long but around 5-6%, such as Daylight Pass (21km, 6%), Townes Pass (27km, 5,6%), Dawson Saddle (38km, 5%) and the various sides of Rim of the World Highway (toughest being 20km @ 6,4% by my reckoning) - a possible exception is Little Bald Mountain, or "Alternate Route 14", which is 23km @ 6,5%, but that is way off the beaten track in northern Wyoming.
There are quite a lot of real HC types if you go for climbs that would have to be MTFs - as well as Pikes Peak (31km @ 6,6%) you have the likes of Mount Baldy (if climbed all the way, not the climbing part of a different side, then descending part of the toughest side, then climbing the same part of a different side then doing the last bit to the finish like the Tour of California did) which is 21km @ 7% albeit with the steepest stuff at the end, and a bunch of the climbs in eastern California a bit too far away from population centres for the race to have bothered with, such as Onion Valley Road (21km, 7,5%), Whitney Portal (19km, 7,4%) and from Wofford Heights east of Bakersfield you've got Alta Sierra Ski Resort (16km, 7,8%), although I suspect the Tour of California would have gone over Greenhorn Summit (the pass below it) from the much more gradual western side. As for steeper PASSES there's only really Palomar Mountain (20km @ 6,9%) and Gibraltar Road that really stand out as HC types that are that for steepness rather than length there, even if lots of other climbs are debatably or certainly genuine HC. Sure, there are plenty of more 'normal' HCs that are MTF only too (Horseshoe Meadows, 31km @ 6%, or Wolverton Ski Area, 33km @ 5,5%, stand out here as tougher examples), but that's typical in Europe too, there are plenty of big climbs that only average tempo grinder levels that are used as summits in Europe too, such as La Toussuire, Val Thorens, Arcalis, Cervinia, traditional Sierra Nevada, or most of the Catalan climbs like Vallter2000, Pla de Beret or Port-Ainé.
Elsewhere in the States you have e.g. Mount Washington (12km @ 11%, an absolute monster), Mount Equinox (8,4km @ 11,7%), Powder Mountain Resort (11,5km @ 9,7%), but most of the toughest passes tend to be long but around 5-6%, such as Daylight Pass (21km, 6%), Townes Pass (27km, 5,6%), Dawson Saddle (38km, 5%) and the various sides of Rim of the World Highway (toughest being 20km @ 6,4% by my reckoning) - a possible exception is Little Bald Mountain, or "Alternate Route 14", which is 23km @ 6,5%, but that is way off the beaten track in northern Wyoming.