The original Manifest Destiny was a belief that God gave Americans the right, will, and purpose of controlling America from the east to west coast. In 1890, America finally reached this goal. Naturally, Americans still wanted to expand more, so the main change in manifest destiny in the 1900s was that America expanded beyond the borders of its original continent and into the Pacific. From this, some believe Manifest Destiny has never stopped, because the base idea of Manifest Destiny is to expand.
I hope this helps, it's what I remember from APUSH. If you need an example, in 1950 Hawaii became the 50th state, and how even after Cuba became formally independent in 1902, America still stayed in a position of dominance, which angered Cubans since America originally was supposed to help them escape tyranny, not become their new tyrant.
