Is it a sin to work in USA?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

The ruling on the lawfulness or unlawfulness of what a person possesses depends on the work itself from which the money is earned. So, if the work is lawful then what is earned from it is lawful and if it is unlawful, then what is earned from it is unlawful as well. This ruling is common to Muslim countries as well as non-Muslim countries. But, in non-Muslim countries, it is more common to get unlawful earnings, like Riba (interest and/or usury) which is almost in all dealings. So, the Muslim who is compelled to live in USA because of a dire necessity should seek lawful earning that is free from what is forbidden. If he does so, then there is no objection for his profiting from it.

Allah Says (what means): {Say, "Who has forbidden the adornment of Allah which He has produced for His servants and the good [lawful] things of provision?".} [Quran 7:32]

Allah also Says (what means): {It is He who made the earth tame for you - so walk among its slopes and eat of His provision - and to Him is the resurrection.} [Quran 67:15]

For more benefit on Muslims living in non-Muslim countries, please refer to Fataawa 81142, 86405, 88291, 377986, 81642, 369667, 81464 and 89879.

Allah knows best.