Income tax: should I work under or over 6 months?

It looks like you believe you can get back your taxes paid in Argentina by declaring yourself a non-resident. Let's assume it is possible.

The catch is that by declaring yourself a non-resident here, you automatically become ineligible to foreign income exclusion in the USA. So, you will have to pay taxes from this amount in the USA.

Whom do you want to inform? AFIP knows how much taxes you have paid.
Ah yes. I'd forgotten you Americans don't have a dual taxation agreement with Argentina
And it looks as though I won't have to file anything to the AFIP:

"The tax year for individuals is the calendar year. Individuals whose sole income is in the form of employee compensation are not required to file an individual income tax return for the year. Instead, their employers are required to withhold income tax monthly, and this tax is considered final."
And I believe I won't have to declare my upcoming American income to the AFIP since I am a permanent resident in the USA and am officially leaving Argentina.