what if earth became the largest planet in the universe

Doubling Earth's Size
Doubling Earth's size would expand the polar radius and thin the atmosphere. However, the planet would still closely resemble the Earth we know.
At Three Times Its Size
At three times its size, drastic changes begin. The Moon rapidly approaches, and its fragments surround Earth, causing massive sea level rises that submerge most continents. Over time, the planet stabilizes as debris is absorbed into the atmosphere, and some of the lost land reemerges. North America remains in place.
Expanding Earth to the Size of Jupiter
Expanding Earth to the size of Jupiter transforms it into an entirely different world. The vast oceans may not even be water, and landmasses nearly vanish.
If Earth Grows to the Size of the Sun
Finally, if Earth grows to the size of the Sun, it ceases to be a planet altogether. The immense gravity and density cause it to collapse into a neutron star, emitting intense energy. Even the Sun itself is thrown into chaos, orbiting wildly around the now-collapsed Earth.