Follow along with me on this:
1) Bilbo, like the elves, "passed into the West" at the end of the Lord of the Rings trilogy. This was during the age of Middle-Earth, implying that it eventually came to be our Earth.
2) Tolkien, as a Briton himself, thought of Middle-Earth as the forebear of Europe. This means that if Bilbo and the elves went west on a great ocean, they eventually came to what would become the continent of North America.
3) His time as a ringbearer, while not good for his soul, did confer upon him extended life. There's no real way of knowing how much extended life would be granted; it's possible that he continued to live for centuries or even millennia.
4) His time as an adventurer granted Bilbo unique skills and talents that could, potentially, be called upon by others in need of a thief.
5) Although he's a skilled thief and an above average combatant for a hobbit his age, Bilbo would need protection if he was going to go on some sort of "mission" for the government.
This leads us to 6) Bilbo Baggins teams up with John McClane to save the United States from the last descendants of the orcs.
Summer 2016: Bruce Willis. Ian Holm. "Old Hobbits Die Hard".
...I'll start running now, shall I?