I am a U.S. citizen that did some freelance work for a Canadian company. They paid me in USD. What tax form do I need?

You don't need a tax form.

To enter your self-employment income not reported on a 1099-MISC:

1. When in your account, select the Take Me to My Return button on the main screen.
2. Type Schedule C in the Search box
3. Select the Jump to link.
4. Answer the general questions about your business (or select Edit at the work summary screen).
5. At the Let’s get income for… screen, select Other self-employed Income.

Or, if the jump to feature does not work:

1. On the TurboTax left menu, select Federal.
2. On the top select Income & Expenses.
3. Scroll down to Self-employment income and expenses.
4. At the Let’s get income for… screen, select Other self-employed Income.
5. Continue with the onscreen interview until complete.