Many American Christians, and some of their opponents, consider the inclusion of the phrase "under God" a crucial issue - either way, a threat to somebody's religious freedom. As a Biblical Christian I see other problems.
The first 20 words of the Pledge are unobjectionable, since God has ordained authorities and we owe them allegiance, of the conditional sort seen in Joseph, Daniel, and others in the Bible.
Trouble starts right away thereafter. First, all the praise that follows implies that the allegiance involved rests on the excellence of the republic in question, with the implication that if such excellence is lacking, such allegiance can and should be withheld. This is a basic tenet of the religion of revolution, which is why revolutionary regimes, starting with the US and down to the various modern totalitarian states, are always praising themselves and demanding the adulation of others. Being revolutionary, having overthrown someone else for not measuring up to their own standards, they must forever deny that they might be no better than those they overthrew.
From that basic lie proceeds all the rest of the lying, because lies beget lies, as we see in any 4-year old. If being under God has anything to do with recognizing His authority and doing what He says, the United States is not and never has been under God, and with all its religious patter has had no more interest in being so than the scribes and Pharisees who, when they robbed widows' houses, for a pretense made long prayers.
This is no more than Jesus said to expect. You can't serve God and Mammon. The US, like all other nations as Jesus said, has always been about the pursuit of and worship of Mammon. 90 years of slavery after their revolution, of the most total betrayal of the principles they claimed to hold dear, was the rather large sacrifice they made to this god, and they have made many such sacrifices to it ever since. The gods you really serve are known by whom you sacrifice to. How much has America sacrificed to obtain wealth and power, and how much to perform the words in the Sermon on the Mount? Work it out for yourself, and you will see what gods America has been under all this time.
Liberty and justice for all of course doesn't even pass the laugh test. The "Christians" who can let such blasphemy proceed from their mouths obviously don't believe what they say about the injustice of abortion, as they stand on 4000 corpses every day in order to praise the "liberty and justice" which they are thereby confessing has been done upon these innocents. And of course they avert their eyes from much other injustice at the same time, as they always have. Did they learn this behavior from Jesus and the prophets?
True worship, as Jesus said, must be in spirit and in truth. There is no other. It's no surprise that demonic worship is about lying. The lying is not incidental - it's the sacrifice of our humanity demanded by whatever evil spirit we worship. Stalin did not receive adulation because people were mistaken about him, but because the willingness to confess what they knew to be the lie was the assurance to Stalin that the worshiper was willing to set even truth aside to be loyal to Stalin. And that's why the creed of American civil religion is all about lying. The spirit of American messianism, which demands that we consider America the light of the world, the city on a hill, wants to know from us that to be loyal to America we will repudiate truth. Christians who serve this idol specifically repudiate the truth that only the real disciples of Jesus are God's city on a hill and that only He and they are the light of the world, the only nation that is or ever was under God.
For most people, truth is worth flinging in the street in order to
show
loyalty to their gods. I'm glad to report that the God I serve,
who
made heaven and earth, does not demand a choice between Him and truth -
in fact, He's the only one out there who is chosen precisely by
choosing
truth and rejected whenever we reject truth. Many do think
they're
serving Him when they reject truth supposedly for His sake - but then
Jesus
did say the days were coming when those who kill His disciples will
think
they're doing service to God. Many of those will think they are
Christians,
as we've already seen for nearly 2000 years.