There is a Marklin store in Stockton CA. AC Eurotrains. He does mail order.
https://www.aceurotrains.com/

I would add to the list RJFTrains as a Stateside supplier.

I have gotten a lot of stuff from Walter Menzel at Euro Rail Hobbies and he is an absolutely top notch dealer. Unless it has changed since my last purchase Walter actually runs and tests every loco before shipping it. You don't get that kind of service very often anymore.

But over the last few years the fees for buying out of country and the incredible increases in shipping costs have forced me to look within the US. If you are anywhere but in the US Euro Rail is highly recommended.

I buy from several US sources but the great service and prices I get at AJCKids keeps me coming back to them.

Guy is very knowledge and they will get you anything from a whole train to any part you can find a number for.

They also have one of the best websites in the MRR business and always respond to your email questions.

You seem to be in a similar situation to me where there is no Maerklin dealer within 300 miles (or more).
Due to that, I have to rely on online orders. I have a few trusted dealers that I frequently do business with.
It depends on your interests. I do a lot of business with dealers in Switzerland for harder to find Swiss models and I have sources in Austria and Germany as well.
My collection is not only Maerklin, but also includes brands like Roco, LS Models, ACME and others as my focus is Switzerland and international trains that can be found on Swiss rails.

If you let me know your focus, I can perhaps find you a dealer or two that can help in that particular aspect.

My recommended dealers in North America:

Eurorailhobbies (BC Canada)
AJCKids (Texas)
Euromodeltrains (NJ)
RJF Trains (NY State)
Reynaulds (IL)
Helmut's Hobbies (VA)

I have heard about AC Eurotrains (CA), but have never ordered from them

My recommended dealers in Europe:
Memoba (Vienna Austria)
Huenerbein (Aachen Germany)
Eyro (Interlaken Switzerland)

Regards

Mike C

Somebody pays for shipping from Marklin De. to Marklin USA before our dealers recieve orders. I suspect it's built into the dealer cost invoices. If any US dealers order direct and bypass Marklin USA, then I don't know, or if that affects any warranty service. Orders from Canada to the US shipping is much higher than from domestic dealers.
Reynaulds in Illinois charges a flat shipping fee of $15 per order, but prices are a bit higher genearally.
AJC Kids charges the std. USPS or UPS ground shipping wirth orders up to $100 insured and over $100 insured for a nomnal fee. Same for Micro-Macro-Mundo in Miami Fla.
I've bouight quite a bit from them as well, but before new owners aquired it last year due to the fathers ailing health. I just havn't needed much.
I don't know why the son(s) didn't just keep it, but I think was on board yet as a cosnultant last I heard.

Then that is fairly recent for Eurorail Mike. I bought my 29000 MS 2 set from them in 2020, and the shipping was via Canada post to Washington State then to me. It was $55 US. Outrageous even then.

Walter moved the shop from the Vancouver suburbs (Langley) to Summerland in the BC Interior/Lower Mainland a few years ago. He makes USA shipments via USPS from Oroville, WA, about an hour's drive away from Summerland. He's still a complete pleasure to work with. I've found that 1) due to availability in Germany from manufacturers, and then 2) the shipping delays from Germany to No. America, it can take a while for any out-of-stock-but-backordered items to reach him; he then consolidates and ships from Oroville. His website is very detailed about availability and shipping so I've never felt surprised. Patience is key, but if I need something urgently and it's out of stock at Euro Rail then I need to search elsewhere. fwiw, he doesn't markup shipping costs but just passes them on.