hast increased [yacaph] the nation [gowy], O LORD [Y@hovah], thou hast increased [yacaph] the nation [gowy]: thou art glorified [kabad]: thou hadst removed it far [rachaq] unto all the ends [qetsev]
of the earth ['erets]. KJV-Interlinear
15 But you have increased the nation, O LORD, you have increased the
nation; you are glorified; you have enlarged all the borders of the land. ESV
The nation being referred to, is the nation of God. Israel is the earthly designation of Gods chosen people, but those chosen people are not limited nor determined by genetics, but by faith.
Gods nation began with Adam, and will continue to increase in number until the last person in history believes in Christ.
When that is, only God knows.
But as far as nations go, and given that there have been perhaps trillions of people born into this world over these past several millennia, then Gods nation will be the largest by far, of all the nations of the world, in all of history.
Removed to the ends of the earth means to have its boundaries extended.
And Gods national boundaries are not limited to time and space, but across time, across geography, and across into eternity.
Gods national boundaries have no limits, but reach across all of the known world, across all of history, and far beyond.
No leader, no people, have or could ever match that growth or reach.
No leader, no people could ever match that sovereignty.
Only God, and more specifically, only Christ, has that capability and authority.