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.