This turned out pretty easy, but enjoy anyway.
The grandest of canyons is found within me;
few can match my nature's diversity.
The continent's largest metropolis I boast,
along with a long stretch of Pacific coast.
Beside me a massive saltwater gulf lies
and I possess some Caribbean isles.
I think that these clues are sufficient, mates.
Tell me the name of these united states?
Looking for the name of a country.