The time frame isn't that important, but do we have records of an independent nation asking to become a district/state/subservient region to a larger nation? Like if Aruba asked to become a Canadian Province?
edit: Thanks for the examples. Now for an add on, what about non-neighbor countries? Texas joined the US and they had a common border, anything further away?
Depends on what you mean. Including both mergers and joining as a subordinate territory:
Spain remained a de jure personal union of Castille and Aragon until ~1715. So they didn't technically become a single country until then.
There is, of course, the United States (the 13 colonies) itself, as well as the Republic of Texas joining the Union.
Yemen from North and South Yemen in 1990.
The United Arab Emirates in 1971.
Tanzania in 1964.
The UK in 1707 (England and Scotland) as per the 1707 Acts of Union.
There is also the German Empire of course. As well as the East Germany joining West Germany.
Newfoundland joining Canada in 1949.
Unification of India/Pakistain as they incorporated the former princely states of the British Raj into their new nations.
In the vast majority of cases these are nations that share a border, yes. However, that is completely to be expected, as nations that share borders are the ones most likely to share cultural and economic/strategic/political structures and interests which would facilitate merging/incorporation. That is why, for example, the thought of Canada joining the US is, although very unlikely, not nearly as ridiculous as the thought of Russia joining the US.
As a follow-up question - didn't Bulgaria ask to join the USSR at some point? If the answer is yes, what happened there, and why didn't it join (or wasn't allowed to)?
(Edit - fixed a typo)