US visitor visa
Dummy ticket for a US visa.
The interview is about your ties, not your flights.
Where the decision is actually made.
Quoted from the State Department's own visa pages.
“Section 214(b) of the INA presumes that every B-1/B-2 applicant is an intending immigrant.”
“That you have a residence outside the United States, as well as other binding social or economic ties”
“Your travel itinerary and/or other explanation about your planned trip”
Note what the third quote names and what it does not. A travel itinerary appears on the supporting-documents list. A purchased ticket, or a booking, does not.
So should you bring one?
It can help. It cannot decide.
The supporting-documents list asks for your travel itinerary or another explanation of your planned trip. A clear document setting out your route and dates is a reasonable way to give that, and it is easier for an officer to read than an account given under pressure at a counter.
What it will not do is answer section 214(b). That presumption is about your circumstances at home, and it is met with evidence of a residence you are returning to, work you are going back to, and family and finances that hold you there. No flight document speaks to any of that.
So bring an itinerary if it makes your plan clearer, and do not buy a fare for it. The flight itinerary is built from real scheduled flights and holds nothing with an airline, which is the honest shape for this use. The verifiable flight reservation exists for applications that specifically ask for a booking somebody can check.
Nothing here guarantees visa approval, entry, or acceptance by an embassy, airline or border authority. Requirements are set by the authority assessing your application and can change, so check yours with them directly. Read the product disclaimer.
What goes wrong.
Usually, asking a document to do a person's job.
Buying a ticket before the interview
The decision is made at the window, often the same day, and it can go either way regardless of what you have booked. A paid fare adds nothing to the case and everything to the loss.
Expecting paperwork to answer 214(b)
The presumption is about you, not about your documents. It is answered with residence, work, family and finances, which no flight document can stand in for.
An itinerary that does not match your answers
If you say three weeks with your sister in Chicago, the document should show three weeks and Chicago. Being contradicted by your own paperwork is worse than bringing none.
Treating the itinerary as the application
It is one line on a supporting-documents list. Bring it if it makes your plan clearer, and put your effort into the parts that carry weight.