Someone's faith says something about their knowledge about the world around them. For example a Young Earth creationist or literalist for president could be very bad if he quoted scripture to show that after the great flood, Earth would no longer be cursed by God, therefore we have nothing to fear from climate change. You may find this example unrealistic or ridiculous, but an actual congress member said this! In a hearing about climate change!! He got his Bible out and quoted it and nobody had him restrained and put in a mental institution!!! Nobody even laughed out loud!!!!
The western world, and especially the U.S.A., is in deep crisis. I'm not talking about the financial one, but the theological one. It is so politically correct to believe in religion, and so politically incorrect to criticize such beliefs. Some beliefs are of course exempt from that political correctness - a presidential candidate claiming to believe in the Prophed Muhammad being God's true prophet, or a candidate admitting he's an atheist, can just forget running for president.
I think that a president actually believing in magical underwear, and that Jesus will run his new kingdom from U.S. mainland, and that they will get a planet when they die, is a major problem!
As long as delusion is defined as "a belief held with strong conviction despite superior evidence to the contrary", then all religious beliefs are, per definition delusions.
And I think that having a delusional president is a big problem, and their delusions should be called out and discussed and ridiculed whenever possible.