Yes, it is literal. However, Catholics and 1/3 of Evangelicals believe it is symbolic. That position is called amillenial. It started with Augustine around 400 AD. Early church leaders all believed it was literal.
This is THE biggest reason the WT experienced so much success early on.... most Christians hadn't heard the "kingdom message" as explained by WT and they ended up getting duped into rejecting the new covenant "for the forgiveness of sins" described in Mt. 26: 27-28.
A literal Kingdom is embraced by 2/3 of all Evangelicals. However, the Kingdom message is still primarily a future message that will be preached during the Great Trib.
The message during the church age (age of grace) is to be reconciled to God:
2 Cor. 5: 18 Now all things are of God, who has reconciled us to Himself through Jesus Christ, and has given us the ministry of reconciliation, 19 that is, that God was in Christ reconciling the world to Himself, not [a]imputing their trespasses to them, and has committed to us the word of reconciliation.
20 Now then, we are ambassadors for Christ, as though God were pleading through us: we implore you on Christ’s behalf, be reconciled to God.