You will need to file a form 1040 as a resident of the USA and be taxed on world income -- this is for the period you were present in the USA. If you had income from the USA sources thereafter that also needs to be included in your filing. The issue here is that it is unclear from your post, if you went through a process to cancel your visa before leaving USA -- if you have then the above is true because thereafter you became a Non-Resident Alien. If you did not , then USA will claim your world income through the end of the year and give you tax credit for any taxes paid to Germany ( i.e. the portion taxed by both countries ).
You can use TurboTax to file your return -- will need a US issued card ( with US billing address ) to pay for the services. IRS can direct deposit / debit from your US bank account ( it is very strongly recommended and now hoped that you have a USA bank account active for at six months past your leaving the country ).
Is there more I can do for you?
Namaste ji
