Is my 401(k), 403(b), or TSP considered an IRA?

No,  401(k), 403(b), and Thrift Savings Plans (TSPs) are different from IRAs. For more info see What's a qualified retirement plan?

When TurboTax asks you if you have a traditional or Roth IRA, answer Yes only if you actually do have have a traditional IRA or Roth IRA, regardless of any 401(k) or other retirement/pension plan you may or may not have.