If you used Turbotax you probably used the wrong program.  If you have only been in the US less than 183 days, then you are a non-resident alien, unless you have a green card, in which you are a dual-status alien for 2018.

A non-resident alien needs to file form 1040-NR.  Turbotax does not include this form. Turbotax partners with Sprintax although there are other competitors that offer the 1040-NR.

If you are a dual-status alien this year, things are even more complicated.

I suggest you should see an experienced tax professional to prepare the correct amended return.

To your original question, if your e-filed return is accepted by the IRS, you do not need to also mail a copy.  In a few rare cases, you may need to mail selected pages with a cover sheet to the IRS after e-filing.  If this happens in your case, you will be told to print instructions and the cover page.  But you need to fix your main problem first.