Since you have passed the Substantial Presence Test for the year, you are a resident alien for tax purposes for 2018. (a) even though you had earnings before you entered the USA, and assuming that you were not a resident alien for tax purpose prior to entering the USA in May 2018, your actual tax year starts from the date of admission -- thus any earnings received before entering the USA, is not subject to US taxation nor any foreign tax credit accrued prior to this date. You file a normal resident return i.e. form 1040 covering world earnings ( except for the period 1st Jan through date of admission ); (b) all earnings ( no matter the source or type ) are treated as if earned in the USA and taxed by the USA { obviously any foreign sourced earnings that are taxed by another tax administration is eligible for foreign tax credit--- treaty conditions may apply here ); (c) as a US resident you are subject to FBAR and FATCA regulations --- thus you must file form 114 at FinCen-- it is an online submission and generally due by the due date of form 1040 without regard to extension.
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