Not really, no. You can change the point of sale country without a VPN by selecting it on the United website (same place you choose language). This will change the inventory and potentially prices you see.

United will revalidate your itinerary, and reprice it if necessary, based on the billing information you provide. The POS will be your billing address.

You can potentially get access to different pricing (inventory) by using a different point of sale. An OTA domiciled in a different country is a common approach for this. It's quite rare for the US POS to be cheaper, but to access a US POS you could book through an OTA's US .com website.