From The Hill:
Addressing Adm. Robert Willard, who commands the Navy's Pacific Fleet, Johnson made a tippy motion with his hands and said sternly, "My fear is that the whole island will become so overly populated that it will tip over and capsize."
Willard paused and said: "We don't anticipate that."
Like other islands, Guam is attached to the sea floor, which makes it extremely unlikely that it will tip over, even if there are lots and lots of people on it. Guam is 30 miles long and up to 9 miles wide in certain spots, with a population of 175,000 civilians. The military is proposing the addition of 8,000 U.S. servicemembers and their families.