The form of Christianity existing today isn't really Christian but instead a part of the Mystery Babylon religious system?

Yes. And America will be destroyed in less than two years by nuclear war.

Some manmade "Christian" churches come dangerously close to that. But the one Church Jesus Christ founded still teaches the fullness of God's truth after 2,000 years, just as He promised it would.

1) The form of Christianity existing today isn't really Christian but instead a part of the Mystery Babylon religious system?

Not according to the Bible.

Indeed: there is no "Mystery Babylon religious system" in the Bible

which clearly and explicitly teaches

that "Mystery Babylon"

symbolizes a city

(rather than some imagined "religious system").

2) Christianity as most people would consider it, the mainstream church is still in captivity to Mystery Babylon's doctrines and customs?

Again: that seems to contradict plain and clear Bible teaching.

Mystery Babylon.  It is an older kind of belief but I haven't heard that since I stopped listening to that White Power Preacher out of Idaho on short wave radio.

He thought that the remnants of the 12 tribes moved to England and then to the USA.  For all that he didn't like modern Jews much. 

Um...if you say so

Now this:

🤮🖕

Many have come to believe that a Christian has a role to play in the political fabric of society. To do that, most believe, a Christian must at times subordinate certain aspects of his beliefs to the will of the society in which he lives. 

For example, many people pay lip service to Christ’s teachings of love and peace, while at the same time supporting vicious wars.For the same reason, churches may encourage their followers to pray for the Kingdom of God but at the same time lend support to rulers who act oppressively.

This counterfeit form of Christianity is not the religion that Jesus established. Rather, it is a man-made version and is practiced by most professed Christians today. 

This version of Christianity has indeed failed, as evidenced by the widespread disregard for Bible principles in all of Christendom today.