When you say "living abroad", I assume you mean your permanent residence is abroad, but you are currently in the US. That is because you only have I-94 form while in the US in the non-immigrant status.
Then, the next thing to look at is whether you meet the substantial presence test:
If you do, then you generally need to file your tax return, subject to filing requirements, such as your annual income. Also note that some visitor categories are exempted, as detailed in the link above (for instance, those on F or J visas).
If your I-94 form has expired, then you are overstaying and are out of status. That, however, does not affect your filing requirements.
Once you leave the US, I-94 becomes a record of your past visit. Its expiration date is irrelevant at this point, other than for the purpose of determining whether you overstayed. Regardless, your filing requirement is governed by whether you meet the substantial presence test. This means that you may need to file tax return after you have left the US.