I am American. I will be traveling from Shanghai back to the US. Can I get TSA Precheck while abroad?
My 1-year-old son is also American. Same situation and question. My wife is Chinese. Same question.
TSA Precheck only applies to security checkpoints operated by the US Transportation Security Administration (and, at some US airports, checkpoints operated by contractors on behalf of TSA). At non-US airports, another country's airport security authorities are responsible, and they do not recognize TSA Precheck.
If you simply wish to enroll in TSA Precheck overseas for your use when you are in the US, you will need to complete the application and visit an enrollment center. As best I can tell, there are no enrollment centers outside the United States. A workaround is to apply for another Trusted Traveler program, such as Global Entry, which speeds your entry through US immigration and grants TSA Precheck benefits. There are Global Entry enrollment centers in Canada and Qatar. If those don't work for you, you'll need to enroll after you return to the US. You can do that in the immigration area when your flight gets in with Enroll on Arrival now (this requires you to go through the application process and be conditionally approved in advance, you can't just roll up and do it), though the benefits like TSA Precheck won't take effect immediately, so you wouldn't be able to use it for a connecting flight right then and there.
Note that TSA Precheck membership is only open to US Citizens and Lawful Permanent Residents (other non-members may receive Precheck benefits on their boarding passes, though that will be happening less often now). Global Entry also allows citizens of some other countries, but not Chinese nationals.