Can I enter a single W2 entry if I have two W2 forms from the same employer?

I want to look at this from the view of the employer, I know that most of the w-2 forms I have seen have space for two states, but in the year 2020 I would expcet that the number of people with 3 states could be higher than normal.

From the IRS: General Instructions for Forms W-2 and W-3 (2021)

Boxes 15 through 20—State and local income tax information (not applicable to Forms W-2AS, W-2CM, W-2GU, or W-2VI).

Use these boxes to report state and local income tax information. Enter the two-letter abbreviation for the name of the state. The employer's state ID numbers are assigned by the individual states. The state and local information boxes can be used to report wages and taxes for two states and two localities. Keep each state's and locality's information separated by the broken line. If you need to report information for more than two states or localities, prepare a second Form W-2. See Multiple forms. Contact your state or locality for specific reporting information.

Multiple forms.

If necessary, you can issue more than one Form W-2 to an employee. For example, you may need to report more than four coded items in box 12 or you may want to report other compensation on a second form. If you issue a second Form W-2, complete boxes a, b, c, d, e, and f with the same information as on the first Form W-2. Show any items that were not included on the first Form W-2 in the appropriate boxes.

In your question you state:

Second one does not have entries for the federal information, and only information for my previous state where I lived for the first half of the year.

That means that the forms you received are correct.

The only difference between the two forms, besides the State information in Boxes 15 through 20, is the Box D (Control Number). The difference between the two control numbers is a single digit, 1 and 2.

according to the same IRS webpage:

Box d—Control number.

You may use this box to identify individual Forms W-2. You do not have to use this box.

The control number is for the benefit of the company. Even though it seems they should have used the same number in box D, the IRS doesn't require anything in box D.

I would combine the forms onto one entry in the Tax software.