My son is a full time student at Oxford University in England and is not employed by them. However, your software is asking for a Filer's federal ID. Is this his SS#?

Where is it asking this?  For Oxford? Did you try to take a tax credit for education expenses?

1098-T Tuition Statement

If they are not listed as an eligible institution with the US Department of Ed, you will not be able to enter it or take the deduction.  The school would need to have a US Federal ID number

Were scholarships more than tuition?

no he has no scholarships

Here is a list of schools that qualify for the Tax Credits.  If the school does not qualify for the tax credits, then you would not enter the 1098-T on your return. 

https://ifap.ed.gov/ifap/fedSchoolCodeList.jsp

https://www.irs.gov/credits-deductions/individuals/earned-income-tax-credit/eligible-educational-ins...

This was not something I determined.  I just listed the tuition he paid to Oxford.  The school is not in the U.S., so I am confused as to why they would have a Federal I.D. # in the U.S.

They probably wouldn't.  But, since they issued you a 1098-T, it was a remote possibility.  You will just need to delete the form from your return.  If they do not have a Federal ID, you cannot take any education credits which means there is no reason to enter it on your return.

To delete it you can go back into the education section and click delete next to the 1098T or you can click Tax Tools>>Tools>>Delete a Form >>Delete next to the 1098-T

University of Oxford does have an EIN and will provide a 1098-T upon request. I just completed my program at Oxford. Their EIN is 98-6001062. You can reach out to their US Loans team and ask them to provide a 1098-T.