"Can we get a PDA diagnosis in the US?"

In short: Yes!
Even though PDA is not in current diagnostic manuals such as the DSM5, it can be diagnosed as autism, with a note in the report about fitting a "PDA profile”
When the DSM-5 was updated to the DSM-5-TR, the ASD 299.00 (F84.0) autism entry was modified so that specifier conditions accompanying a diagnosis of ASD (autism spectrum disorder) no longer required diagnostic codes. Therefore, PDA can be included in a diagnosis of ASD 299.00 (F84.0) as a specifier. The medical diagnosis for PDA is ASD, and ASD is a protected disability.
Other specifiers include sensory processing disorder (also not in the DSM), hyperlexia, catatonia, etc. 
But not every diagnostician (person who diagnoses) is going to be aware of PDA. There are also practitioners who have outdated ideas of what autism "looks" like. Many PDA people demonstrate social skills beyond what is expected, so it takes more current training to properly identify the autism and the PDA.

FINDING A PDA-AFFIRMING PROVIDER

Our group maintains a list of providers who submitted their information to be included on a list. This list has all kinds of providers who offer various services like coaching, occupational therapy, counseling, diagnosing, and more.
*please be aware we cannot guarantee any outcomes, and we do ask that you vet any professional to be sure they understand what PDA looks like, and let us know of bad experiences so we can remove non-affirming providers*

Our PDA-Affirming List

Helpful Pointers:

PSYPACT STATES
Normally a person can only use services based on what state they’re in. For instance, if I am trying to get assessed in Oregon then I can only get assessed from someone licensed in Oregon. Historically to get assessed in another state I would need to travel there.
A growing number of states however are passing legislation to become a “Psypact” state.
Psypact honor licenses from other participating Psypact states. So if I’m in Texas (psypact state) I can shop for practitioners that diagnose in Florida, or Idaho, or Nevada, so on because they are also psypact.
To see if your state participates in psypact, click the first link on this Google search for the full map:
INSURANCE
It is worth it to find the right assessor considering it can take months, if not years, to finally be seen. But not every assessor is going to be covered by your insurance, what then?
If you have private insurance you can often get assessed by someone out-of-network and still pay a lower cost. Talk with your insurance provider for more details.
IF YOU HAVE AN OPEN MINDED PROVIDER
If you already have a team of people working with your child that are open-minded to learning more about supporting PDA, the following links lead to printable documents you can share with them.